What kind of free promotional tools should I use as a tanning salon?

Answer 1

Is your goal to get more clients or more visits from existing clients?  That seems to be a key distinction.

If you want new clients, you might set up a computer at the counter and ask clients to recommend & review the business on Stik.com.  (You could give them a coupon for their trouble.)  All recommendations and reviews are automatically shared on Facebook, and in general ~15 people see each one.  Quite powerful.