DEFINITELY remember that you're not their friend...

This applies especially if you're working with older kids, but it goes for all ages as well: PARTICIPATE! There are going to be SO many kids who don't like certain activities. They don't like sports, they can't do the craft, they hate the idea of hiking, they're scared of horses, they just don't FEEL LIKE doing whatever it is you're doing.

Do it with them! You'll be amazed at how many of them really get into it!

A few years back I was taking my group to sports... I have never been a sports person, and I really wasn't feeling it that day, so I asked the sports director if I could slip over to the office to get our mail... and maybe take my time there. She said no, and I sighed and said okay.
We played floor hockey, and I got so into the game that it completely astounded my campers (who knew I wasn't into sports). Now it's one of my favorite things. If I happen to see a group playing floor hockey, I make a point of asking to play (gives some tired counselor a break too), and the kids like playing with adults who are really excited about the game!