I haven't done a freeze before, but I often will do a freeze per category ---meaning, I won't let myself buy another something until I use something I already have of the same category....so, for example, if I already own ink sprays I won't let myself buy more until I have used up the ones I have or use them more often. Thus, when I see something I want or is a good price, I will sometimes see how it relates to what I have at homes and if I notice that I hardly use what I have of the similar item at home, then I'll know I might not often use this item either. Patterned paper is a GREAT real-life example of this for me....
Another thing I ask to myself --- unfortunately this is usually after I bought things----is: "if someone told you it will cost $15 to enter Michaels to shop, would you go?"----now of course no one would pay $15 to just look in Michaels w/o taking something out of the store and sometimes I add that also to the statement ("and you can take out 2 items from the store...")....but what I am usually noticing is sometimes I just wanted to browse and didn't expect to spend $15, thus after those instances, I think "if I had know it'd cost me $15 to enter the store...." Sometimes when I think this way, it helps me think do I ~really~ want what I got? and then I can go from there for future purchases from what I learn of myself.......I hope that all made sense... (There has been many times I didn't expect to buy a thing and was so glad I found some item and thus I WAS happy to spend $15!)
I often look at clearance items similar to what Kathy said about trying one thing before buying more---I buy things on clearance to try to see if I'd like it first before buying more. I also get to know the stores' clearance routine and then just wait for the right price etc....but I am fortunate b/c I am able to visit other stores when visiting family and can compare and wait/watch products.
But one thing I wanted to say is that ~sometimes~ while I am waiting for a lower price etc, I will figure out I really don't need or care for the item like I thought and thus I move on....which reminds me of something I read for buying things you WANT---the article said that when you find an item you want, to leave the store and go about your routine for a day or two and see how often you think of the item again----and there has been times I never thought about it over the next day or two so I know I probably didn't want it and was just being influenced buy the marketing stuff Daniel was talking about.
One thing my mom used to say about clothes when I was younger and I would tell her I'm not sure about a shirt---she'd say "well if you're not sure, then you probably don't really want it"----and I have used this idea for when trying to decide craft items to get.....I noticed the things I really like, I don't have to try to decide if I want it/will use it or not---I already know I will!