First you have to make a few decisions. Here are just a few.
How low do you want to go? Without an idea of what you are looking for, it's hard to tell you what you need.
What kind/size wheels are you going to be running? If you're running the stock 15" wheels you have to be careful with certain brands of drop spindles.
What's your budget? This is usually the deciding factor for the previous 2 questions