After 6 or 7 workers, built depot or pylon at the choke point (entrance). Continue to pump out workers to mine. The key is flow of money coming in. Terran is barrack and then bunker behind the depot for the start. The time you can relax is when you are able to make medic so your guys seldom die. Always place an SCV or two at the bunkers to repair when under attack. For protoss, there's two approach. One is to be able to build cannons first. The other is offense all the way, with at least two barracks starting. Play with comps first on Bnet with teammates to practice. The key is mining, you can have two workers per block of crystal.