There should be a pair of guys going to the left, a pair going to the right, (in flanking positions of course) and however many team mates there are left should go into the middle so that your offense will form a U around the other team. And if needed, you can call in for backup and the person in the back should answer the call.
Even though this is just a general over view on what type of positions there should be, there should also be specific positions. One person, who is the sniper, should obviously be in a spot where he can shoot easily and be under heavy cover. The crawler should be somewhat near the middle, moving with extreme caution, with the fear that someone will see you. The crawler is the one who shoots down the enemies moving from bunker to bunker or shifting sides of the field.
Here are some examples of good positions:
The man on the left has the advantage... HE HAS COVER!(except for the fact that he is going to be shot in the head) The man who charged him is now in a bad stance, which gives the man on the left the easy kill. All he has to do is move to the left or right and shoot him. Since the one on the right is already looking over the bunker, he won't see the man on the left come out from the side of it. Easy kill, always stay in cover.
The wrong way to be in a bunker
The reason that this is the incorrect way to be in a bunker is because, as you can see, he isn't facing the bunker straight on. Which means whatever way he is turned (in this case, to his right) he is unprotected on his backside (his left) and is also unable to move/react to situations that may arise because he can't see on that one side. When there is a tall bunker, you should face it just like the man below is doing.
The correct way to be in a bunker
The main thing that is key about being in a bunker, in this position, is that you have all options to shoot at. In the "wrong position", the picture above, he could only shoot in the way that he was facing; while in this picture the man can shoot at people to his left (which he is) or his right. A little mistake like entering a bunker the wrong way can get you killed.
Laying down is sometimes better
In a bunker like this one, it is wise to lay down rather than kneel. As you can see the bunker drops on the right side. If he was kneeling using just the cover that the bunker gives on the left side of itself, he would have two weak spots. Large portions of his body would be exposed on the right side, while the same goes for the left side of him. It was a good choice for him to enter that specific bunker laying down. Just make sure that when you do this, you have a man guarding your 'blind spot'. (Read: The wrong way to be in a bunker, if you don't know what I mean by blind spot) NOTE: Laying down rather than kneeling or standing depends on the bunker. The bunker above is a laying down bunker.