1. Tell parents to put kids in clothes that can get wet, because even if they don't try to get wet, they will.
2. Dress yourself in clothes that can get wet, because even if you don't mean to get wet, you will.
3. Those kiddie fishing poles that are supposed to be "tangle proof", aren't. Try for a "Huck Finn" sapling pole with ten feet of line and a worm. Simple. Probably just as likely to catch anything as the more "modern" pole.
4. Have a second set of gear ready when the traditional fish poles are all out of commission - like cotton string and chicken livers to catch crawdads with, or nets to catch tadpoles with. Or even butterfly nets.
5. Make your scouts bring their own lunches. You don't really want to roast hot dogs at the same time they are fishing. Seriously, you're going to be untangling lines and pulling stray hooks from clothing. You won't have time.
6. Sunscreen, sunscreen, sunscreen and more sunscreen. And bug spray. Gallons of it.
7. Better yet, don't attempt the fishing at all and leave the fishing for the Scoutmaster when they turn 12.
8. Okay, you know that #7 only applies until a parent comes up to you and says, "My son had so much fun fishing with you. When are you going next?"
9. "The worst day fishing is better than the best day working" is subject to interpretation.
10. Stay out of the rocks. The rocks take your hooks and the crawdads take your toes.