Most places will tell you that they need to be kept in a cool dark place. You also want to keep them in airtight containers. So spices that come in opaque containers such as tins generally hold their flavor longer than ones in clear glass. Storing them away from heat sources such as the stove is usually the best idea. Inside a closed cupboard or in a drawer where they won't get light on them helps too. That being said, you'll probably want to keep some of the most used ones like pepper where you use them the most frequently.

Here's info from a spice company: http://www.tampicospice.com/faqs

Here's info from the Food Network: http://www.foodnetwork.com/how-to/articles/7-tips-to-organize-your-spice-rack.html

I have a lot of spices (way more than would fit in any spice rack) since I experiment with a lot of international foods. I keep mine in individually labeled bags filed in 2 accordion file folders with handles. They stay so neat, take up so little space, and are always easy to find now.