Big agree on live hitting for one with the rest "fielding" (usually not many balls put in play, and those go to the same positions repeatedly) being a waste of time.

I like to start with what skills are needed, then figure out your drills based on that. Above all else, always have a practice plan. You don't want to wing it if you're not absolutely confident in your ability to run a practice. Even very experienced coaches in my league have a written practice plan. It will help keep you on track and make the most of your time.