Now that you know a thing or two about playing guitar, here's some more intermediate and even a few advanced tips and tricks of the trade you could find useful.
1) Tremolo picking, otherwise known as rapidly alternate picking. Basically, picking up and down as fast as possible, thus playing the fretted note repeatedly in succesion. This technique is often used by Dick Dale, Dave Murray, Adrian Smith, and Edward Van Halen, and was the basis of main riff in the Iron Maiden song Wasted Years. Tremolo picking is also common in mandolin playing and flamenco guitar and the technique was picked up from violin players rapidly running the bow back and forth across a string. It sounds as if the player is letting one note ring, but that note is broken up in a staccato sequence. Try to make each note sound as even as possible.
2) Diatonic scales. Since we spoke about major and minor pentatonic scales, I should tell you about the major and natural minor diatonic scales, also known as the Ionian and Aeolian modes. These scales involve a full seven notes. In solfege terms, the major scale is do re me fa sol la ti do and the natural minor scale is la ti do re me fa sol la. In terms of steps, The major scale is Tonic, whole step, whole step, half step, whole step, whole step, whole step, half step, and the natural minor is Tonic, whole step, half step, whole step, whole step, half step, whole step, whole step. In scale degrees, major is 1 major2 major3 perfect4 perfect5 major6 major7 1, and minor is 1 major2 minor3 perfect4 perfect5 minor6 minor7 1. These diatonic scales are considered the most used scales in music and the natural minor is highly popular in heavy metal.
http://en.wikipedia.org/wiki/Diatonic_scale
3) Harmonic and Melodic Minor. The reason I refer to the minor scale as the natural minor is because it is the naturally occurring minor scale of the key, no accidentals. Now there are two other forms of minor, the harmonic minor and the melodic minor. The harmonic minor has a raised or augmented scale degree 7, or a major7 rather than a minor7. The raised 7th acts as a leading tone, which is supposed to lead to the tonic. The melodic minor has a raised 6 and 7 or a major6 and major7. In key signatures, neither the harmonic or melodic minor are naturally occurring and both require accidentals. They each have unique and exotic sounds to them and are often heard in heavy metal, classical music, and neoclassical shred.
http://en.wikipedia.org/wiki/Minor_scale
4) The blue note, also known as the tritone. The tritone is three whole steps from the tonic, or a raised or augmented scale degree 4, or a lowered or diminished scale degree 5. This is often used as a passing note in blues, rock and roll, and heavy metal lead guitar melody lines. The blues scale is nearly identical to the minor pentatonic scale, but it includes the blue note. This is probably the most used scale in blues and rock music. The first heavy metal band Black Sabbath are known for their use of tritones. Tony Iommi's guitar riffs would often accentuate the tritone for both a bluesy effect and an ominous and semi dissonant sound. Historically, the tritone was banned from compositions and deemed "the devil's interval" due to it's characteristic dissonance. Now it can be used to create soulful and flavourful guitar solos.
http://en.wikipedia.org/wiki/Tritone
5) The Modes. These are exotic scales used often in progressive rock, jazz, fusion, classical, neoclassical shred, and certain types of heavy metal. The secret to the modes is playing the major or minor scales and moving the tonic and key to a different scale degree. There are many historical modes, but the naturally occurring ones are the most common ones we use in present day. In scale order, the naturally occurring modes are Ionian, Dorian, Phrygian, Lydian, Mixolydian, Aeolian, and Locrian. For example, if you took the major scale, put the tonic on scale degree one, it would be the Ionian mode, with the tonic on scale degree two, it would be the Dorian, on scale degree three, it would be the Phrygian, and so on.
http://en.wikipedia.org/wiki/Musical_mode
http://en.wikipedia.org/wiki/Properties_of_musical_modes
http://www.dinosaurrockguitar.com/new/node/800
6) A guitarist walks into a dive bar. Ouch. Bad joke, or useful guitar tip? Take a look at the bridge. Some guitars come equipped with a dive bar at the bridge, also known as the whammy bar, the tremolo arm, or the vibrato bar. The dive bar can be pressed up and down lightly to create vibrato, or it can be pressed down hard to dramatically lower the pitch, also known as a dive bomb. Jimi Hendrix, Jeff Beck, and Eddie Van Halen have famously used the dive bar. Some guitarists like to shake the dive bar while trilling a note to create a warble effect. Some play a pinch harmonic or a natural harmonic and shake the bar or dive bomb. Some dive bomb and then scoop into a fretted note. Some tremolo bars, such as the Bigsby are more suited to subtler vibrato, and others such as the original Floyd Rose are equipped with a locking nut and bridge for tuning stability so you can do the most outrageous dive bombs and stay in tune. Some tremolo bars are floating bridges and thus can be used to both drop and raise the pitch of the strings, but floating tremolos can have less sustain and thinner tone, whereas flush mounted tremolo bridges have the same sustain and tone of a hard tail bridge.
http://en.wikipedia.org/wiki/Vibrato_systems_for_guitar
http://en.wikipedia.org/wiki/Floyd_Rose
http://www.floydrose.com/
7) Playing with a slide. Blues and rock guitar players are often known for playing bottleneck or slide guitar. I've already told you about sliding up and down the neck with your fret hand fingers, and now I'll tell you about using a slide. A slide is a cylinder in which you can fit any one of your four fingers in and use it to slide up and down the strings, usually worn on the second, third, or fourth finger. Duane Allman, Mick Taylor, Keith Richards, and Robert Johnson are known for playing slide guitar and you can hear Slash play slide in the solo for Rocket Queen in standard tuning and throughout the song Bad Obsession in a form of open G tuning. Eddie Van Halen plays slide in the song Dirty Movies. You should try your best to mute the strings while using a slide because it creates a lot of string noise.
8) Alternate tunings. Open tunings are mainly used for slide guitar playing so you can slide all the strings in tune with each other, though some player slide in standard tuning as well. Open tuning means tuning all the strings so each string is part of a chord. For example, open E would be tuned from the sixth or thickest string to the first or thinnest string as EBEG#BE, open A would be tuned as EAEACE or even ACEACE, open G would be tuned as either GBDGBD or DGDGBD, which is the tuning used by Slash on Bad Obsession and used by Keith Richards with or without a slide. Keith Richards doesn't use the sixth string, therefore his tuning is GDGBD. Jimmy Page has used DADGAD for songs like Black Mountain Side and DGCGCD for The Rain Song in the studio and EADADE for the same song live. Drop D tuning is just tuning your sixth string down a whole step from EADGBE to DADGBE. This has been used by many types of players from Neil Young in the song Cinnamon Girl to more extreme metal and nu metal players for it's lower, heavy, bassy quality, thus they also often use sven string guitars and detune them. Classic heavy metal and hard rock songs in drop D include Unchained and Sinner's Swing by Van Halen and Lay it Down, You're in Love, and Lack of Communication by Ratt. Tuning down a half step flat to EbAbDbGbBbEb is common, and has been done by Jimi Hendrix, Tony Iommi of Black Sabbath, Ace Frehley, Eddie Van Halen, Joe Perry, Randy Rhoads, Warren DeMartini, George Lynch, Slash, and Stevie Ray Vaughn. It loosens the strings and allows for easier bending and some would argue it sounds crunchier. Tuning down a whole step to DGCFAD is also common and is done by Mick Mars of Motley Crue, and you can sometimes hear this tuning used by Randy Rhoads, Tony Iommi, and Criss Olivia of Savatage. Ian Chains of traditional heavy metal band Cauldron tunes to CFBbEbGC as well as Criss Olivia which is uncharacteristic of traditional heavy metal, which uses mostly standard tuning or down a half step. Alternate tunings allow for playing in different keys and different chord voicings. The disadvantages are that it may be hard to get used to when you've been playing in standard tuning and that you may have to go up or down string gauges.
http://en.wikipedia.org/wiki/Guitar_tunings
http://en.wikipedia.org/wiki/Drop_D_tuning
9) String skipping. Instead of playing linear scalar runs up and down a pentatonic, blues, or diatonic scale or mode, you literally skip strings and jump ahead to a note further up or down the scale. This was popularized by shredder Paul Gilbert of Racer X and Mr. Big. You can also hear Slash play this in the main riff of "Sweet Child of Mine." I'm not personally that good at string skipping, so Wikipedia will probably explain it best. Here's where you start heading into extreme metal, jazz, and neoclassical shred territory.
http://en.wikipedia.org/wiki/String_skipping
10) Sweep picking. This technique was popularized by neoclassical player Yngwie Malmsteen. A lot of shedders use sweep picking as a cop out, but it can be used quite tastefully when done right. To sweep pick, you pick down or up across the strings in one sweeping motion, often while playing an arpeggio. I'm no good at sweep picking, but I do sometimes rake the strings. Raking is one way sweeping and often with muted strings for a percussive effect. Practice raking muted strings, downward or upward, then practice raking arpeggios, then move on to full up and down sweeps.
http://en.wikipedia.org/wiki/Sweep-picking
11) Multi finger tapping. This technique has been used by primarily shred guitarists. It involves fret hand hammer ons and pull offs forming the bass notes and pick hand tapping sometimes involving all four fingers forming the treble notes. Eddie Van Halen would often attach a board to the bottom of his guitar to raise it to a horizontal position in order to play the guitar fretboard like a piano. Stanley Jordan, acoustic guitarist Andy McKee, shedders Buckethead and Bumblefoot, and Reb Beach(of way too many bands) have very highly developed tapping styles. One thing Eddie Van Halen did very differently from his early schtick was the recorded intro to Mean Street, in which he used tapping purely rhythmically by tapping the top two strings with his first finger and the bottom string with his thumb and muting with the left hand, then going on to tapping harmonics.
http://en.wikipedia.org/wiki/Tapping
12) String muting. The gift and curse of electric guitar is it's sensitivity. It's designed for total ease of use and is thus much easier to play than a classical guitar and arguably easier than a steel string acoustic, but due to it's highly sensitive nature, it picks up extraneous string noise and more mistakes than either classical or acoustic. No matter how well you can play or how many techniques you know, without proper string muting it will cause extraneous string noise and sound sloppy. Basically, lightly touch the strings that aren't in use with your fretting hand or press down with your pick hand palm to mute the strings.
http://en.wikipedia.org/wiki/Palm_mute
Now that I have told you about oh so many guitar techniques, and you can tell me later if I've missed any, I should let you know something. Playing electric guitar isn't about having perfect technique and there's no such thing as good or bad technique. Playing guitar is more about the sound. Does it sound good? In that case it works. Does it sound bad? In that case it doesn't unless you use it to your advantage like Eddie Van Halen. Having "good" technique may make it easier and more comfortable to play guitar, but having "bad" technique can be part of your guitar playing character and feel. Also, you may be able to shed and use sweep picking and string skipping really well, but can't bend or slide and stay on key. Work on making your playing more tuneful and soulful, more passionate, dynamic, and melodic as opposed to just shredding and showing off. Try working on individual techniques one by one until you have gotten good at one, then move on to the next. This is a great article about just that.
http://www.dinosaurrockguitar.com/new/kb/playing/technique/learning