1. Buy what is on sale and will be durable. If you put my sale priced shoes alongside someone who invested a lot of money in their shoes, if they get scuffed or lost, who is going to be more upset? Did you ever notice how people that spend a lot of time shopping and finding products can sometimes go on and on? I think this is a result of how much they've invested in them on the front end. It became a hunt instead of a gather. (for a look at obsession balanced with truth, watch Amy Adam's movie!!!)
2. Recognize when you're buying something for the beauty of it and find beauty somewhere else. For me, at one point I realized I had WAY more stationery than I'd ever use. I told myself I was going to use up my stationery before buying anymore. It was great! I could look at the different beautiful papers, but I didn't need to buy them. I used up paper that I didn't care for as much, telling myself that the message I was writing was more important than the pretty paper. To find beauty, start a collection of clippings of ideas and colors and look at them for fun. Not every idea has to turn into a purchase - it can be an artistic expression and be just as satisfying.
3. The thing that has helped me squash materialism the most is the song, "The Wondrous Cross" (contemporary version :) There's a part in the song that says,