My program provider did their best to have me prepared for everything. I had lists of things I had to show them (police check, working with children's check etc) and they gave me the option to do first aid training with them or do my own beforehand. They organize the placements and hands-on training and help with visas as needed. They are always contactable and give you plenty of info beforehand. They are flexible with placements so these may change last minute but often it's a case of they simply ask if you'd like to do more.
Be prepared to adapt. You will be tired, the weather may change, plans will have to be altered due to changing circumstances and that's just part of the fun and spontaneity. There will be children whom you instantly connect with and are easy to get along and there will be challenging ones.
Daily tasks include morning sports/activities, waking the kids, depending on their ages, helping to get them ready for breakfast, breakfast, more activities, lunch, different activities, dinner, something fun after and then bedtime. You can learn different sports of the world, yoga, high ropes, geocaching, archery tag, even Quidditch, swimming and BMX riding. There's also daily teamer meetings and a relaxing campfire every night.
My biggest fear was having a problematic child in my group or just a child who I couldn't get along with. The language barrier was also a bit daunting as my German isn't great, I've only learnt for a few years in high school. This did happen and I simply had a chat to teamer manager who helped me deal with the situations as they arose. I tried to have a few one on one conversations with the child and I simply tried my best to make her feel wanted and comfortable within the group as best as I could.
There's a great team around you, if you are desperate to catch up on some sleep or aren't feeling well just let your other teamers (leaders) know. At training we are taught how to run big group activities, this allows teamers to get some R and R as needed. The best thing to do is to tell someone :-)