Be assertive and commanding. If you can't control your models you wont get anything done. I personally hate photographing people, but sometimes it is part of my job. Groups are the worst though. If the models are good and you talk about what you want out of the shoot they might be able to help and give you options on different poses on their own.
Do some research for what you are shooting to get an idea for a variety of poses. You can tell that sometimes the photographer has no idea what they were doing because every photo looks the same. Maxim photographers are pretty bad at this. I've seen a few magazines where the female celebrity (who is an actress/singer and not a model) does the same damn pose in every shot and they just change the background and wardrobe. Think sitting, one arm between legs, slight squint and mouth slightly open.