I don’t know if I exactly agree with all of these rules since I love to thrift when I’m not looking for anything in particular. However, these are great guidelines for the thrifter just starting out. (from thriftcore.com)

1. Not bringing your Thrift List.
Take inventory your needs and wants.
2. Not being in the thrift mood.
If you’re not in the mood, you won’t make the passionate thrift love and find mounds of thrift goodness. You have to have creativity and see the potential in the piles of thrift store junk. You have to be in the mood for thrift loving.
3. Buying it just because it’s cheap.
If you won’t use it, don’t buy it. If you don’t need it, don’t buy it. If you are not going to resell it, don’t buy it. Only buy what you’re passionate about.
4. Paying more than the item is worth.
You may want a thrift or antique store item with all your soul, but stop and think first. Can you find this at another store for a lower price? Is this item really going to change your life? Is this a rare, hard-to-find item? Don’t impulse buy.
5. Buying what you won’t use.
If you’re not going to use it, don’t buy it. Kind of like the art piece but not enough to hang it? Take a picture and move on.
6. Rushing Through the Aisles.
Take your time slowly going through the aisles. Go through each box, go through the stuff others won’t, like a dusty or dirty box. This is where the real treasures lie. If you rush, you’ll miss them.
7. Giving in to retail.
You may think you’ll never find the exact piece your looking for. Maybe you’re looking for the perfect couch or side table. If time isn’t a factor, don’t give into retail. Don’t pay hundreds or thousands when you can get an item for dirt cheap or even free.