I have a small cabinet that's away from heat above my counter that I store my spice jars in. I try to buy the smallest containers of new spices or spice blends that way if I don't like them it's not a waste of space or money. My daughter brings glass baby food jars over and fills them from what I have. It helps her to save money. The more popular ones that I use all the time I buy in big containers from Costco.
I buy my favorite spices from Penzey's because I find them to be so much stronger and fresher. They last a lot longer than the stuff at the store - who knows how long they've been there!? They come in ziploc bags and I take out small portions and put them in small glass spice jars I buy at World Market. For spices I use rarely, I'll either try to buy a cheap bag from the Latin section in the grocery store or the bulk bins at our natural food coop. I also buy our everyday spices at Costco, like Montreal seasoning or garlic/onion powders, since I know they are fresh and I go through them fast.