Just my added 2 cents...
CoD4 is a little to fast paced for true house to house clearing, but the principles are still all the same... below is a copy/paste from one small section of the TG SWAT SOP:

Movements:
-Hallways: Teams of two move down a hallway, officer 1 directs the movement, while officer 2 is slightly behind and just right of officer 1. Any doors on the left are covered by 1 while doors on the right are covered by 2. Both officers NEVER cross in front of a door or area without clearing it first.

-Staircases: Teams of two moves up or down stairs, 1 watch up or down in the direction the team is moving, officer 2 walks backwards covering the rear or high ground. Unless there is another team to cover the rear while that team moves up and clears the stairs. You stop at the top or bottom of the stairs (depending on direction moving) while the element re-stacks.

Stacking:
Stacking up on a door or entry is the most important key to proper room entry. A "regular" stack is 1 at the left side of the door, 2 on the right, 3 on the left side behind officer 1, and 4 on the right behind 2, (1 and 2 enter together, then 3 and 4 together.) A "stack left" is where you stack in a line on the left side of a door in numerical order. "Stack right" is the same but stacked on the right of the door. Usually when one side is a danger zone and unsafe to be on that side.


Basic Entry:
A basic entry is where there are no known contacts or subjects on the other side. Officer 1 opens the door, enters going left, with officer 2 right behind him. Then officer 3 moves in and goes right, followed by officer 4. The all clear is given for each room.

Specialized Entries:
Specialized entries are when you know or think there’s a subject or hostage in the room. These are default combat entries but the first officer in ALWAYS goes strait to the known contact. Then the back up officer goes opposite, covering other danger areas.

-Button Hook: A button hook is where officer 1 enters and goes left and stops on the left side of the inside of door covering 9 o'clock. Officer 2 enters and goes right, just inside the door and covers 3 o'clock. If more officers, then 3 enters and goes left covering 10 o'clock, followed by 4 going right and cover 2 o'clock. Your all close to the door, you don't go in deep, just within 5 yards of the door. But NEVER block the door.

-Criss Cross: A criss cross is where officer 1 enters from the left and goes kind of strait to the right side of the inside door, covering 3 o'clock, followed by officer 2 from the right to the left covering 9 o'clock. Other officer’s criss cross, 3 from the left to the right to cover 2 o'clock, and 4 from the right to the left to cover 2 o'clock. Criss cross is a faster entry because your moving strait, but dangerous with a teammate walking in front of you.

-Starburst: A starburst is usually used when entering a big area, it’s the same as a button hook, but you move further into the room, and each 4 man officer covers 1/4th of the room. You move into the room in order, you get to the center of the room, and your backs are all together. 1 covers 6 o’clock (the door you entered) to 9 o’clock, 2 covers 6 o’clock to 3 o’clock, 3 covers from 9 o’clock to 12 o’clock, and finally 4 from 3 o’clock to 12 o’clock.

-Penetration: A penetration entry is another large room entry. All officers enter; move down to position on the entry wall, and then all face and cover 12 o’clock. Then in a line formation and upon the element leaders command you move slowly towards 12 o’clock clearing everything.
1 enters left of door and moves all the way down wall to the left, 2 follows stopping halfway between 1 and the door, 3 then enters and goes right all the way down, then finally 4 enters right and goes halfway to 3 and the door. The Element Leader then takes the door position.

the full document:
http://www.tacticalgamer.com/swat-4-...gamer-sop.html

I know there has been a couple of times I was playing and said to a partner standing next to me:
"Button Hook, I'll go left, you right, GO!"
and he was like "HUH?"

With just you and a partner (2 man team, in any tactical game, you should never be alone), as your moving to an objective or target, enter and clearing buildings, simply slow down... just a tad, and at each door someone say "Button Hook, I'm left" (the other will know to go right), or Criss Cross (good for seeing someone in a corner faster... but don't get stuck in a door way, caller always goes first (since no time in CoD4 to assign stick numbers.)

JMO...use it or don't.