rabbit:
In my experience, a movie is a safe bet -- you can't go wrong, because they will probably enjoy the movie or if not that then the movie popcorn. It also won't put too much pressure on you to impress, since the movie takes up a big part of your date.
On the other hand, a movie can make for a less memorable date, as it is pretty ordinary, and also doesn't give you as much time to talk. If you go to a movie then it might be wise to plan it so that you can have dinner afterward. Then again, you said you are already friends, so you probably know her pretty well already.
The danger in going fishing, as Trust did, or several other like activities, is that the girl may have a terrible time if she doesn't like the activity or if it's too hot/humid out =/
But maybe there's something creative that you'll know she'll be enthusiastic about, that's not too out of the way. (If you make it too out-of-the-way she might be scared away and/or put in the uncomfortable position of feeling guilty that you took so much trouble.)
As you see, there are no rules, there only guidelines. Judgment is everything. If you're ever in doubt, just think what Joe would do, and do the opposite. If you need more advice you can always AIM me.