Now this is the secret to using terrans correctly, taking their defense and ability to build structures anywhere, and using it offensively. When you have about 8 marines, take 2 scvs and construct 2 bunkers outside of the opponents base. This will first ensure that he doesn't escape nor will he expand. Now you can rally all your units to this point, as long as there is no other exit. Soon build an engineering bay, to protect against lurkers (optional).
Now you should try scouting and see if it's clear to bunker further up ahead. Also sunken colonies have a longer range than bunkers so building too close will be a waste. If possible you can try to take the player out with all your marines, but you would need more than 12 if he has an adequate number of hydralisks. If you take heavy damage, try sending more scvs, since this is the key. Now start construction of a factory behind your bunkers. This will make tanks right on the battle field, as comapred to inside of your base. Make sure to get siege mode before building a tank. Soon you'll have your first tank, allowing you to do some damage.
Carefully siege up next to your bunker and wait for your next tank to be built. You should also build an academy to get comstat to further the distance of your tank. During this time you should keep building marines, scvs, and supply depots.
Soon you'll have enough tanks to cover your scvs as they make more bunkers.When they are completed fill them up, and un-siege the back row of tanks and more them up. Leap frog your way into his base.
