Since Ghost Recon isn't exactly SWAT 4 when it comes to CQB and I pretty much play alone, my approach may be rather gamey.
If I can take shots through windows without putting myself right in harm's way, I do take 'em. If there are multiple ways to enter, I tend to pick anything but the main entrance. This door gets covered by AI in case contact is made upon opening it. I position myself next to the door and wait a moment in order to pick up any noise. I open the door and either wait for my good people AI to kill bad people AI or I peek around the frame, ready to open fire. Stand up, make entry and try to sweep any corner where I would expect an enemy to hide. This way, I work myself from room to room.
My, err... "tactics", involve dying and quick loading. A lot. Of course it helps to carry a handgun or anything else with short stabilisation time, preferrably with a suppressor. In case there is nobody to rescue or capture, portable boom-heat-shrapnel-generating devices might help also.