#1
OK, I've been in a band for just over a year now, and i feel i haven't contributed as much as i should be, music wise. But i can't seem to write music for the life of me. It's either already been done, or i just don't think it sounds to good. Any tips on how to write effectively and efficiently? I'm also not to good with my theory, so if i come up with a riff or something that i like, i get stuck.
#2
Here's a quick basic outline for ya'. Don't take this word for word, but rather read it and then go do your own thing with this stuff as suggestions.

1. Choose a key, any key.
2. Read http://ultimate-guitar.com/lessons/chords/what_chords_are_in_what_key_and_why.html to figure out what chords are in that key.
3. Play around with those chords to find a good combination that works well and sounds pleasing to you.
4. Figure out the notes to those chords and make up a riff or lick based off (but not only using) those notes.

From there it's all you man.
#3
Well, learning some theory - even a small amount - will help. My suggestion, before you go any farther with music, every guitarist should know the circle of fifths like the back of his/her hand as well as scales. Try thinking in terms of chord progressions and create riffs over them or, if you find a sweet-ass riff, think of the chord progressions that fit over it and that will make it easier to continue the song.
#4
ok thanks guys! I know very minimal theory, but not enough to know what chords fit over what keys, or even how to tell what keys are which. i will definitely read the article though! thanks again!