After you have chosen a diamond, you are ready to pick a setting and band. This does not require the knowledge that picking a diamond does, it just depends on what you think your fiancé will like. Some examples of different settings include having the diamond jut out or ride low. Jutting out is much showier then riding low, but it may scratch something from time to time. More examples include cluster, prong-solitaire, bar, gypsy, and channel settings.
The most common bands are gold, white gold, or platinum. Take a look at what type of jewelry your fiancé already has to determine which type she might like. But if you can’t decide, silver is very popular right now.