This can turn into a very long topic. As always, it will depend on the players' abilities to a great extent and to some extent, their age. However, I like to do at least two fielding positions in addition to pitching/catching. Keeping in mind that practices are only so long and if you break up into groups to work on position specific skills, you will have a difficult time getting them all in regularly for quality instruction and practice. I try not to look at players and which positions she can play; instead, I approach each position independently and find AT LEAST two players that can play that position. Right or wrong, I start with SS and CF (where I feel we need our most athletic players). I then move to 1B then LF, then 3B, then 2B, and finally RF.
Of course, you will end up with some players that can "fill in" at many of the positions just because they "get it". Also, you may find that you have to put a weaker player in the #2 for any position because the preferred one has to be a #1 at a different position and #2 at yet another. For example, Little Katie may be a better 1B than Little Brittney but Little Katie is already the #1 SS and the #2 CF. IF I need to pull the #1 CF and the #1 1B, Little Brittney will need to play 1B. That is why I start with what I consider "key" positions then move forward from there.
"Release the [OFC] hounds!"