Everyone's style is different but this is what I do (and other pros in my area do similarly):

• Always be respectful of the model.
• Never touch the model, but if you need to rearrange something that you can't get them to do then ask for permission to touch them first.
• Be careful of your wording. If a shot isn't working make sure that you don't make it sound like it's their fault.
• Be direct with your directions. Using hand gestures that show them the tilt and direction to be at is very effective.
• Never go into silent mode. That is very awkward for a model.
• Be professional in your language. Never tell a model they're hot or attractive or something else.
• If the model is doing something good, be sure to mention it. It tells them what's working and gives them a little boost.
• Never blame your equipment or skills for missing a shot. If something isn't working, just change what you're doing but don't make them lose confidence in you by what you are saying.

These are just a few rules of thumb I've learned from pros like Andy Armstrong and incorporated into my people pictures. If I was to boil it all down to what I consider to be the best way of communicating it would be this:

Be respectful at all times and provide good feedback throughout the shoot.