One thing she doesn't mention is that you should take a list of sizes and color preferences, both for yourself and your family, if you will buy for them. Also, even though most thrift stores here are good about checking zippers, buttons and so on, do the checking for yourself.
I have occasionally bought more than I intended to at a thrift shop or a garage sale, but better that than buying more at a retail store! If I spend $5 on a sweater that I love from a thrift store, it's much, much easier on my budget than spending anywhere from 3 to 15 times that much at a retail store.
Still, it isn't wise to "shop 'til you drop" no matter where you're shopping. One good way to keep yourself under control is to take only cash and leave the checkbook and credit card at home. Then if you find a really good buy or something you really want, you can decide to put back something else, or not. It puts the decision in black and white, instead of being able to use excuses to buy both.