Number One.
Practice your pitching.
Nothing turns me off more than a crappy half-assed bend and vibratos. Everyone in the band is in tune and you'll ruin the whole balance by bending or doing a vibrato out of key. If you can't do it, practice until you get it. The guitar is probably one of the few instruments out there on which you can bend notes. It's to me what makes the guitar so special.
Honestly to me the most important thing for a guitarist is his/her vibrato/bending technique. No one is gonna remember your shredding/"million" notes per second solo. Although sometimes it's nice
But most folks, the laymen out there, remember melodies, soul/spirit and the overall tightness of the band and feeling they get walking away from a performance.
Number Two.
If you're gonna solo, do so tastefully. Remember that as a guitarist, you're role is a supportive one. Backing up the band is important. When you're soloing its your turn to shine. And do so tastefully, plan your solos before hand if you're not much of an improviser. It doesn't have to be technical, or fast or whatever. Sometimes playing slowly and soulfully is the best way to win your audience or compliment a song.
Number Three.
Don't kid yourself. If you suck, you suck. Big deal it's not the end of the world, there will always be another tomorrow to prove yourself
So be it, everyone has their bad days. Take these experiences and work on your playing. It'll only work out good for you in the end. Practice practice practice. And more practice. Work on your weaknesses, don't try to run before you can even walk.
Number Four.
Practice on your own is important, but more important is getting things tight with your band. Work together as a team. Don't just think of your own parts per se, contribute to the rest of the workings of the band. Also it's very important to get the feel of handling an amp at gig levels. I've seen guys on stage who hesistate while playing because they are not used to the amp's volume. A result of playing way too much in the comfort of the bedroom.
Number Five.
This is what IMHO I feel is the most important facet of band manners. Watch your volume. Like I mentioned before...nobody is there to see you, unless of course you're a solo artist. Or your girlfriend is out in the audience. 8)
People are there to see the band. And most importantly the layman out there wants to hear the singer. I've been to gigs and seen singers screaming at the top of their lungs to compete for volume with the guitarist. Very sad.
Folks I hope I didn't sound harsh.
If anyone's interested my band Crossover will be playing at Orchard Cineliesure on Saturday at 12 noon. I do hope I examplify what I just mentioned as to what are the prerequisites for an well mannered guitarist