To clear out a room, stand besides the door, as one of your teammates would have if you told him to clear out a room.
Make sure that your clip is full and the action icon does not have the brackets around it, so your teammates will not open it for you and take fire. Finally, make sure that all of your teammates are stacked up properly:

(for double doors)   _____       (for single doors) ___

               *     *  *                          *  *

                     *                             *  *

Then, rush the room with thermal/night vision (your choice) on and scan left to right for enemies. Then, strafe to the left of the door to let your teammates in. Next, walk around the perimeter of the room and when your teammates say threat neutralized (on some smaller rooms they do not say anything), your work is done.