1. Never yell. The more you yell the less they'll play.
2. Teach basic skills (how to dribble, how to control the ball by stopping and starting, how to kick) by playing games (sharks vs. minnows, follow the leader, do as I'm doing).
3. Have fun. Act silly sometimes, be a little bit loud, and run a lot.

Everything else is gravy. The next Neymar is probably not on your team, so your goal is to help kids be excited about soccer. Some of the kids will keep score at games, others won't. You might end up with the team that has a bunch of big, aggressive kids or you might have the group of kids that run along side the action instead of getting in on the action. Either way if you teach the basics, stay positive, and keep your cool it will be a positive experience for you, the kids, and their parents.