sue there really is no "easy" way to rotate 9 girls in a team.  it all depends on the type of team you have the positions the girls can play.  i have basicaly only 2 shooters on my team of 9, so my shooters rarely get a break. so i rotate the centre players and defence.  some girls get only to play half a game and so be it.  but if i had an even mix of positions then rotation would be a more equal thing.  but you just need to be careful about moving people around too much, as the team never gets to gel as well.  particularly with younger players as they are still learning about where to be, and where to expect others to be.  

if you can give more info on your team dynamics, what you want to achieve this year, how old, and skill base it would be a lot easier to help with a rotation.  sorry i couldnt help more.