1) Have a list. This one is a no-brainer, and yet how many times have we gone to the store "knowing" what we need and coming home with a lot more than that? Make lists for stores other than the grocery store.
2) Do not take your children with you if you can at all help it. When they are little they just don't like shopping, and that is okay. But their misery will spill over to you and you might buy things you didn't really want, or you may forget something and have to go back.
3) When you do take your children shopping with you DO NOT teach them that they can pick something out because they were good (or because they whined, which is worse). If you grocery shop with your children weekly this is 52 items per child that you have purchased. If you buy them candy then that is 52 candy bars or bags of candy, and they just don't need it. Likewise, don't buy them junk toys from the dollar store just because they are cheap (and the children whined). Don't buy them something every time you go to Target.
4) Do not shop recreationally, and don't teach your children that shopping is a form of entertainment.
5) Likewise, don't teach your children that shopping is such a chore that they deserve to be rewarded for it.
6) Do not take children into toy stores or toys sections of stores to browse. If you aren't there to buy something then don't take them! This really is just mean, and it sets you up for meltdowns that you deserve.
7) Likewise, don't take yourself into stores to browse, especially if it is a store full of items you have a hard time resisting, such as fabric, yarn, books, kitchen gear, etc.
8) Do not buy your child a toy just because you are picking out a gift for a friend or sibling. This teaches a bad lesson and takes away from their opportunity to learn how to give. The focus should be on the other person, not the child; how can their minds be on thoughtfully selecting the best possible gift for a friend when they are thinking about themselves?
9) Don't get fooled by marketing. If a supermarket is selling limes 5 for $1 and you only need one, then buy one for 20¢. Know that not all end cap items are priced on sale. Pay attention to price signs; some grocery stores will put green grapes at 99¢ per pound right next to red grapes for $2.99 per pound. They do this on purpose; you might grab the wrong one and not notice until you are home. Look high and low for lower priced products; marketers often put the most expensive items at eye level.
10) If you are shopping for clothing, wear good undergarments and an outfit that you really like. Smooth underwear and a supportive bra will help you see how the clothing looks on you. Wearing something you feel good in helps you not be tempted to buy something just because you feel frumpy.
11) Go to thrift stores first! Almost anything you need is probably available at second hand store.
12) Be flexible. If you have low heeled black dress shoes on your list and come across a great pair of black flats at a thrift store, ask yourself if black flats will serve the purpose you wanted the heels for.
13) Plan your shopping wisely. People often hear not to shop hungry, and that is good advice, but you should also time your shopping so that you don't run into meal time, thus keeping you away from home when you should be preparing your meal and instead tempting you to get food out. If you must be away from home all day for shopping be sure to pack a cooler with your meal. I like to pack snacks if we will be out longer than two hours.
14) Speaking of coolers, take one with you if you will be going to several grocery stores and the weather is warm. You can take along ice packs or sometimes ask the store for ice in a plastic bag (if they are a store that puts items on display over ice). You don't want to risk anything spoiling, as that would be a waste of your hard-earned money.
15) If you see something that you really want, take a picture of it (if you have a cell phone). I do this with books and then order them from the library if possible. I also use the photos to jog my memory at the thrift store; a photo of a mannequin with a cute red t-shirt and jeans reminds me to look for cute red t-shirts at the thrift.