1.) Know your role.
Are you accompanying a singer? Playing in a chamber group? Laying down the rhythm in an r&b group? Naturally, guitarists want to make the guitar the most important instrument in the ensemble. Don’t have this mindset. In an extreme case you might risk losing work. If you have trouble judging, just ask.
2.) Play what you hear.
Don’t try to take up too much space. Space will let the music breathe. The pursuit of music leaves us with many possibilities, but you don’t need to play all of them in one tune.
3.) Leave space.
This is the easiest way to make contrast occur in music, especially when there are a lot of notes in the air.
4.) Interact with the other musicians.
Don’t play in your own world. Look and listen to the musicians around you. Music is a communal sport.
5.) Contrast from the other musicians.
If someone “invents” something (a rhythmic figure, melodic motif, etc.), feel free to contrast from it. This can create tension. Your next step would be to figure out how to resolve it.
6.) Mimic from the other musicians.
If someone invents something, feel free to go along with it. Avoid too much mimicry, though. Don’t mimic so much that everyone does it. You run the risk of losing foundation of the groove.
7.) Play in tune.
What if you’re in tune, but the piano is slightly off? Tune to the piano if it can’t be replaced. The piano may be slightly off, however everything should sound in tune, even if it’s not tuned at 440 Hz.
8.) Play in time.
Rather if your phrasing or comping sits on the back, front or center of the beat, make sure this is consistent. You should be able to tap your foot easily to whatever you play.
9.) Play with groove.
Knowing how to notate and analyze all the complex rhythms in music won’t matter much if you cannot groove, rock, swing or lock into the bass player and drummer.
10.) Don’t play too loudly.
11.) Don’t play too softly.
By not playing too loud or soft, you’re creating a good balance for the ensemble.
Keep in mind all the instruments and parts around you in the ensemble. Never forget that guitarists mainly accompany. Have your playing reflect accompanying, not abandoning.
13.) Solos don’t necessarily need to be loud in volume.
Many guitarists blare their solos. By doing so, it covers up the rest of the ensemble.
14.) Know which registers to “comp” in.
If a soloist plays in a higher register, comp in a lower one. Create contrary motion. This helps balance out the spectrum as a whole when playing with other musicians.
15.) Vary chord voicings.
Play inversions. Play spread and close voicings. Mix these up.
16.) Properly EQ the amplifier to the room and the style of music you play.
Rock tends to be brighter. Jazz tends to be darker and more middle range. In some spaces, the guitar may need to have more brightness to be heard in the ensemble. With the way the EQ is shelved in different amps, you may have to compensate by adjusting a level a little more or a little less. Finding this balance is a never-ending process.
17.) Don’t completely max out the guitar volume knob.
Unless you use a volume pedal or some sort of boost.
18.) Take advantage of using multiple pickup combinations and other timbres.
Many times guitarists overlook all the sonic possibilities of multiple pickup combinations. If you have humbucking pickups, coil tap them so you can use the single coil function (like a Strat). Even if you just use a simple three-way switch for humbuckers or five-way switch for Stratocasters, each pickup has a different sound (pickups towards the fretboard have more bass; pickups towards the bridge have more treble). Also, experiment with playing close to the fretboard or close to the bridge.
19.) Use good cables.
You don’t necessarily need to be an audiophile, but use cables that don’t produce hiss, hum or thin sounds. It’s beyond the scope of this post, but pay attention to the cable’s capacitance. A lower number allows more of the natural brightness to reach the amp. This allows the treble spectrum of EQ to run lower, thus reducing hiss.
20.) Play with the pick.
For some styles, it is best to use a pick (strumming chords, shredding, playing rock, etc.).
21.) Play with the fingers.
When I comp in jazz or another style, I use my fingers more than a pick. Not only can I be more selective with notes and play spread voicings easier, but also I like the sound of it better. It is similar to pianists lifting their fingers up off the keys when playing.
22.) Play to the acoustics of the room.
No room will have the same sound. Some rooms are very dry. Some rooms have a lot of reverb. (By the way, as electric guitarists you should always have a good reverb pedal handy). In rehearsals, play to the room you rehearse in. Listen for balance with each instrument. Most importantly, do not let the acoustics of the room affect your performance.
23.) Don’t over-think and over-analyze.
Nobody can think, judge and play all at the same time. Enjoy playing and use common musical sense.
24.) Make each note count.
Overall, this should become the focal point of your guitar playing.