Basically, keep them orderly and untangled. At the end of the night, tidy them up for the next night. The Sound board folks will cut the volume between sets, so you can detach and attach them without making horrible sounds. If for some reason you have to disconnect or connect during a set, try to alert the Sound board so we don't get a minor explosion of sound. Do not roll the piano over mic cables.
Some folks are really nervous.
Jokes are often appreciated. Many folks are experienced and know what they want. If the setup is not obvious, and they don't tell you what they want, ask them. Likewise, for unusual instruments where the best placement is not obvious, ask them for guidance. Saturday and Sunday afternoon shows.