If it's a hallway: 5 man team (breach team) Alpha team (2), Bravo team (2), leader (1)
Alpha will breach and take kneeling positions on either side of the hallway, giving enough space for Bravo and Lead to deploy into the hallway.
Bravo will take a standing postion behind Alpha. Leader will usually float behind A,B to have a good view of the battle and to direct troops and their fields of fire.
Alpha will cover Bravo by taking a standing stance and providing covering fire as Bravo moves up in Kneeling stance to avoid friendly fire.
You can leapfrog up the hallway doing this.
If there is doorways and rooms that need to be cleared, the forward element would do such, with the rear elements (lead and which ever team) would cover the hallway.
You can do this with largers groups as well, but it would be best to leave the breach teams in groups of 5 for sake of overall room purposes. Stacking too many people in a hallway can be disasterous if enemy 'nades are employed.
timing is key, and room clearing will determine your success in assaulting.
"The Guns! The Guns! Thank God! The Guns!"