Tips & Hints
This is where I have my own hints ans tips, all of them maybe wont fit your style of playing.
Round the house stabbing
I have use this in a few levels (06, 08 for example). When there is a guy so long that he can see you in the dark green zone and there is a small construction do this -> Stand up and when he sees you hit the dirt, crawl out of sigth, then run around the house (or whatever object) and stabb him fron behind.
The get your enemy to you by showing yourself
OK, this is meybe the easiest and most used way of getting your enemy to a sefe place to kill him (everybody should know about this, and I think they even say it in a brief). Stand up and hit the dirt when the sigth comes over you, now the guard (or maybe two) will come running towards where he saw you. Make sure you go behind something that he wont discover you -> when his not looking or on his way back stabb him. Note that if it's a guard with an 'important' guarding position he will shoot instead and cause the alarm.
Taking 2 and 3 man patrols silently
I've got a style how to take down 2 or 3 (maybe even 4) man patrols with the sapper, mariner and beret (not in every case). Choose a place on their path where you have good access from and to a hideout. When they've passed put the mantrap on the path, go back and get the marine (and beret if your trying on a 4 guy troop, which I've never tried). When the first fall down by the trap-> sneak behind harponise the one nearest to the body and stabb the last one (If there is 4 use the beret to stabb the last one). You can also use the decoy instead of putting the trap on the path (where someone else migth see you in work).