The basic promotional shot for a band consists of the band members against a neutral background. Ask the band members to wear something slightly similar, but different enough to set them apart from each other. For example, the guys might all wear different T-shirts, with similar shoes or hats.
Arrange the band against a dark background that acts like a frame around the members. Mix different poses to find the right one. Shoot the band from the ground, shoot the band straight on and change the arrangement of the band members.
Take the band members outside and use the natural lighting to your advantage. Choose a gritty background, such as a junkyard, scrap metal yard or abandoned mine. Try different areas, looking for one that fits the band members. Shoot photos of the members goofing around at a skate park, standing on the beach or surrounded by trees. Keep taking shots until you find one that work best.
Rehearsals are considered down time for bands because, while the band is still practicing, the members don't have to put on a show for fans. Ask if you can take photographs throughout the rehearsal. Take individual shots of each member and group shots as they practice. Shoot from unusual angles, such as the back of the room, underneath the band and from above the band. The more shots you take, the more chance you have of finding your next promotional shot.
Take the band to different locations, looking for places that match the type of music they play. Electronic or house bands pair nicely with a neon-lit street or on stage, with lights flashing in the background. Bands that play pop music might prefer taking pictures at a school, playing on the playground. For a heavy metal or hard rock band, shoot the members at a construction site, with the machinery showing in the background.