There are a lot of things you have to consider when choosing FF programs such as:

1) what airline(s) serve your area(s) the best
2) where you think most of your miles will come from (affinity cards, bonuses, actual mileage flown, etc.)
3) do you want to use your miles on flights or upgrades, or what?

I'm sure I'm leaving out a bunch of other factors as well, but I'm going to focus on where you want to go on your award flights. If you want to go to Hawaii (be REALLY flexible) then Delta is not a bad choice because they have award flights for only 30K miles. (Most programs set the award at 35K.) On the other hand, if you want to go to Australia, then DL is not so great cause they nor any of their partners have good, direct coverage of that area. If you are thinking about a trip to South America, then CO has a lot of coverage. Think about where you want to go when you start spending your miles and then start accumulating them in a program that can get you there for a reasonable amount and in a reasonable manner.

yorock