1. Upon entering, ask "Is this a thrift store?" The salesgirl will patiently explain the difference between a thrift store and a vintage store (to wit: thrift stores sell whatever they are donated, from any time period; vintage stores sell items carefully hand-picked from, mostly, the decades prior to 1980). Thirty seconds later, tell the friend you have been on the phone with since you entered that you're at the thrift store.
2. You are, of course, here because you have been invited to a costume party; even odds on whether it's a Seventies party or a Gatsby party. Tell the salesgirl you want either a Pucci print maxidress or a beaded flapper dress.
3. When she explains that those items are rare, expensive and (especially in the case of flapper dresses) basically nonexistent in a wearable size or condition, get extremely huffy. Be sure to dismiss out of hand the half-dozen historically-accurate alternatives you are offered.
4. When the small child you have, for some reason, brought with you begins to get bored/cranky/hungry, do not under any circumstances change your plans to accommodate this. When the salesgirl attempts to distract and entertain your child by inviting them to try on hats, grab your child by the upper arm and order them to wait patiently without touching anything. Repeat every three to five minutes as needed.
5. When browsing, never read price tags. Instead, hold each item up and demand to know how much it costs. Do not show the salesgirl the tag until prompted to do so. Once informed of the price, emit a small, disbelieving huff. Honestly, $18 for a signed piece of 1960s costume jewelry? That's barely less than half of what a lower-quality piece would cost new! Outrageous.
6. When told that an item of clothing is not your size, try it on anyway. In fact, try on as many items as you can, ignoring your salesgirl's recommendations whenever possible. If you pop a zipper or shred an armscye in the process, that is hardly your fault.
7. Do not, under any circumstances, put clothes back after trying them on. Endeavor to leave as many items as possible on the floor, in a pile, unzipped and inside out.
8. Ask if you can put a pair of $5 clip earrings on hold until the weekend. When told there is a 24-hour limit to holds, insist that you will come back for them. Do not give in!
9. Time to make your sole purchase: a pair of $6 sunglasses. Here is where your earlier disbelieving huffs will pay off. Having established that the shop's prices are insultingly high, you may now haggle. Just like you would at H&M.
10. Pay with a credit card. Do not ever come back for the clip earrings, ever, no matter what.