Not all Americans were keen on the idea of rebelling against his Majesty. Thousands of Americans served in Loyalist (Tory) military units ranging from poorly trained militia to highly regarded regular troops; e.g. the British Legion and the Kings Rangers. Estimates of maybe 50,000 troops fought for Great Britian. Estimates of 1/3 of the population, probably closer to 1/4.
Tactics:
Everything from close order linear fighting to light infantry tactics, as well as more disorganized militia actions.