Its not hard. Ensamble did a wonderful job with the game, I think. Its not too different from Age of Empires when it comes to a basic strategy.
The first thing you should to is just build one building, get a few marines and charge the enemy base.
Yeah, that would probably be the best way to go at it...
Well it will kinda be the same thing except we will be controlling many marines, warthogs and tanks at the same time...