1. ***Always*** have more prepared than you need. Make a lesson plan for your meeting, then add one or two items, just in case. This is much like having a Plan B, but a plan B may not be sufficient if the boys finish everything you had planned and there's still 15 minutes before the parents arrive. You do *not* want to be running around the house trying to figure what to do next. You haven't really known fear until you've had this experience. :^)
2. "You must build it before they come". When planning a craft project, it is a good idea to build one first. You'll find out if the glue works well with the felt or not. You may find out that the wood for the birdhouses, or tool boxes is going to split. You'll definitely find out how long it takes to do, which will help you plan meetings. It'll be something to show the boys, so they'll put the piece with the hole for the bird to come in at the top of the house, and they will know what the project is supposed to look like when finished.
3. Expect a level of behavior, and get it. The boys will try to have "more fun" than you'd like, and your job is to make sure they have fun during the game, not during your talking or presenting. *USE* the good conduct candle, the "Signs Up," and definitely start every sentence you want them to answer with "Now raise your hand, who knows..." Because it may seem restrictive and strict, but it's tried and true, and it'll save your sanity.
4. Communicate, communicate, communicate - with the parents. We only have the boys for 4 and 1/2 years. And the program changes dramatically, and subtly during that time. Each year the parents will need to understand the workings of the program, what they need to do to help their son earn the badge, and arrow points. And it'll help you as they grow to get the help you need running the meetings, going Webelos camping, and crossing the boys over to more fun in Boy Scouts.