Just had this discussion with my CPA, a very smart fellow and a friend who sold his business recently (not signs). Both said basically the same things, best bet is to show increasing profitabilty over last few years (should be working smarter the longer a business is running ), including having detailed records. Also having knowledgeable employees that can operate the business so everything does not depend on the owners doing it all (still need some way to transfer owners knowledge base to a new owner in a short time frame, ie proceedures for everything). Basically like everyone else has said, equipment, (at used value), software (all you can get), art work that is transferable, store fixtures (as used value) and some value for the blue sky with many methodes to determine that one.
Basically be ready to adjust what you think it is worth, and put yourself in the buyers shoes.
good luck