Just get a list and lots of pics.. where you sell the stuff people will want multiple photos.. especially guitars.. need close ups on the front, back, headstock *where the tuners are) and people generally like close ups of any damage, which all needs to be documented in the ad or people will lose their minds when it arrives..
Same for amps - try to document any damage.. would be helpful if you could make sure everything works, as well..
Friendship is like peeing your pants.. Everybody can see it, but only you can feel the warmth..