The Starcraft Command
This is a good all around strategy, its might take a while and a good amount of money, but it should work pretty well.
If the player you are playing are Protoss or Zerg, start pumping out SCV's until you have eight. build a supply depot and barracks. When you have enough money make 2 more barracks and pump out marines like crazy until you have 18 or so. Take the marines and 2 scvs down to the persons entrance. Make sure they dont spot you so start a little far away. Have your guys hop from bunker to bunker untill u reach the very edge of their base. While one scv is making bunkers, use the other to make a factory down there with the bunkers to save time it takes for tank to reach. Get siege mode and start bombing away! their units will fall easily, and if they decide to go air fast, build turrets outside their base to keep them in. This will prevent their scouting and expanding. either they run out of money, or you finally overpower them.
Make sure you make those turrets to prevent mutalisks!