Blue Nile suggests finding a band that mimics and enhances the style of the engagement ring. If you get one that is completely different, it might detract from the beauty of your engagement ring. For example, this ornate ring above would go well with an equally fine-designed wedding band (below).
This engagement ring is not quite as ornate as the one above, but still has a lot of sparkle! Give the overall look even more power by pairing it with a band (below) that coordinates so flawlessly with the band of the engagement ring, that people may not even realize they are two separate pieces.
What to do if you are going with a solitaire? Just like the previous two examples, go with a band that reflects the style of the engagement ring. Here, the focus is the solitaire popping out against the sleek metal. Give that solitaire even more value by going with a solid band (below) rather than making it compete with an additional row of stones.