Arrange your songs to suit the acoustic playing style. Strip them down to their basic components of chords, melody and accompaniment. Some sounds simply don't translate well from electric to acoustic. For example, in her acoustic version of "Sweet Child O' Mine," Sheryl Crow elected to forgo the melodic guitar introduction and instead focused her acoustic performance around the chords.
Select songs that complement the acoustic environment. When playing acoustically, you need to project the sound by playing with gusto. Guitar strumming works better than gentle finger picking, because it's easier to do louder.
Select an upbeat number for your opener. This will grab the audience's attention better than a slow, brooding number.
Remove all sound projection obstacles. If you are playing acoustically to an audience, the space needs to be as conducive to acoustic playing as possible. For example, if there is an electric fan on stage, remove it. While a fan won't influence an amplified performance, the gentle humming will compete with the subtle nuances of your acoustic instrument.
Dampen any loud instruments. If you have an acoustic drum kit and you're playing with an acoustic guitarist, place pillow cases over your drum heads and cymbals. Although both acoustic, a drum kit is considerably louder than an acoustic guitar.
Replace any instruments that are too loud. If dampening doesn't sufficiently attenuate the volume of the drum kit, use hand percussion instead of a full kit. Substitute the snare drum for a tambourine and high-hats for egg-shakers.
Attack the guitar strings accurately. Don't use excessive force with the plectrum, but do strike each chord firmly and cleanly.
Use visual cues. If you are playing in ensemble, use eye-contact or predetermined hand gestures to signal "drop outs." A drop out is where all but one member of the band play quietly. This allows the remaining player to solo without competing for volume with the rest of the band. Rather than attempting to play even louder to make your solo heard, a drop out section lets you perform at a comfortable volume.
Start at moderate volume. Give yourself room to increase the dynamics of a performance by beginning at moderate volume. If you start off as loud as possible, there is nowhere else to go if you want to end with a crescendo.