You are coaching an U-12 team. You do not say if this is a skilled team, or an unskilled team, but I’m assuming it’s some sort of house league team, with a blend of some skilled and mostly unskilled players.
You also ask about strategies, but do not mention tactics. Are you interested in strategy (overall methodology for play of the game, such as using passing control play v. using kick and run), or are you interested in tactics you can teach (how to successfully advance the ball in a 2-on-1 situation, for example)?
I would generally coach such a team by building up from the ground tactically. Start with 1-on-1 drills, which serve to teach the players two things (hopefully): that a defender will get beaten in such a situation if they “stab” at the ball to take it away, and that an attacker will be unsuccessful in getting past a defender who is skilled at simply delaying forward progress by the attacker. Then, you can start with 2-on-1 drills, such as wall passes, give-and-gos, overlapping runs, etc., to show the players how to overcome a 1 v 1 stalemate. When they are successful at a few of these tactics, start adding in a supporting defender, converting the situation to 2 v 2. This then is followed by 3 v 2 tactics.
Having gotten this far, you can now start introducing small-sided games that reinforce the drills you have run. Thus, for example, 3 v 3 with scoring done by completing 5 passes, 5 v 5 where each successful give and go is a score, etc. At the same time, you can start to work on larger-scale operations, such as drills on switching the field to encourage promotion of “width”. Keep in mind, though, that large-scale operations have to take into account the skills of the players. It does no good to drill crosses if your players can’t kick a ball in the air more than 15 yards.
As for generalized bromides about how to play the game, useful in almost all situations, I would say many have been already mentioned. I always emphasize that it’s what you do when you don’t have the ball that wins the game. And it is a good idea not to wait for the ball, but rather go and get it, before the other team does. But such bromides can be taken to far, or put to unfocused use. You can often tell when a team has been told to make runs off the ball by watching the people without the ball running aimlessly around the pitch, all upset because the person with the ball doesn’t pass it to them, never thinking about the fact that they are not in a place, or headed to a place, to which the ball can actually be passed without being intercepted. 
One last one: you say “6) Stay in your own position.” I cannot think of worse advice to give a football player. Much of what makes football so wonderful is that it isn’t played with static positions. Brazil have been famous for decades for the overlapping runs their outside fullbacks make up the wings, for example. A better statement is: make sure all positions are covered. That is, if the center fullback is up to engage in a scoring attack off a corner kick, someone (such as one of the center mids) had best be covering for him. 