100-300mm (x1.5) - best soccer spot
For shots at < 1/1000 I'd choose to stay behind the goal line rather close to the corner flag. That way you'll have more action moving towards you.
For shots at > 1/1000 I prefer moving along the side line, and I often end up close the mid field where there is normally a lot of action. Here, the action will move more sideways and higher shutter speeds are required.
In order to capture attacks I'd stay at the side line, but rather close to the corner flag. From this point of view I'm able to follow attackers, defenders + keeper actions.
I always turn off the OS (seems to slow things down).
Oh, not to forget; I largely prefer shooting from a low position. I feel that this gives better proportions to the images.
PS: I shoot children games and I'm normally allowed to move around the outside of the field.
Best of luck