One of the best things you can do to prepare is to write up an agenda for each session. The agenda will include:
If you teach together with an assistant or co-teacher (always a good idea) get together with them at least soon after your last class to plan the next one. Although ideally, you should plan several weeks in advance to give to time to prepare and to reduce last-minute anxiety-related mental blocks. (You know what I mean.)
Include everything – even who will open and close in prayer. Have a copy made for each teacher or helper. Resist the temptation to get by with a spoken, rather than a written agenda. You will find it worth it’s weight in gold.