Please buy a new wig cap. I have seen women, although the signs are clearly posted to buy a new/clean wig cap, trying on wigs with nothing covering their greasy looking hair. Imagine getting some kind of head lice from a wig?!?!
As noted above, most shops do limit wigs to trying on 3; however, if you buy a wig they do tend to let you try on more the next time you come in. My shop of choice allows me to try on a ton of wigs. I even took my mom and sister to the shop and they were allowed to try on more than 3 (mom bought 1 and sister bought 1).
If you do purchase a wig, please wash it before you wear it. I am convinced that even though they claim returns are not an option on used hair, shops and on-line stores to sell their returns wigs w/o inspecting them for wear. I received a greasy, synthetic lace top wig from an on-line vendor.