Good stuff Timber.
As timber said, you'll develope your own style of how to play this over time.
I'm guessing your "D" sucks? (They should be intercepting the passes, or atleast tying up the opposition infront.)
When the puck is behind the net (or behind the goal line for that matter) this is one of the few times you can "look off" the puck to see where the shooters are. If you can keep track of them, you'll have a better chance at stopping that on-timer out in friont.
The way I usually play this is like this:
I always stay on my stick side. By that I mean when the puck and carrier go behind the net I line up on the right post...my blocker side. I place my skate wheels against the post on the inside of the post. Blocker and stick outside of the post with the heel of my stick blade covering the bottom of the post and the heel pointing out towards center ice. Now you've got that side sealed.
Next is your stance, I always stay crouched and low with my legs/pads apart. If you stand up tall with your pads together, it's harder to do any lateral movments. So now your crouched and ready to explode out to the shooter or other post if need be.
Next is keeping an eye on the guy behind the net. Since you are crouched down low you will be able to turn your head to look behind the net. You will be able to see almost completely behind you over to your stick side. From this postion you can see the puck the whole time it's behind the net, and you don't have to worry about poping back and forth from post to post.......and flipping your head around as well. Every time you go back and forth like that you take your eyes off of the puck and take a chance at being out of postion if the guy behind the net tosses it out front while your moving.
At this point the puck carrier has only a couple of options to make a scoring play. A on-timer pass out front, or a wrap a round.
He' not going to try and wrap it stick side since you've got the covered big time. If he tries to wrap it glove side (You'll learn to read the commitment on this.) all you have to do is a short little push over to that side leading with your stick. Make sure your stick blade is facing so that if he comes around and tries to stuff it, the puck will be directed away from the net, not into it....trickier than it sounds.
If he's going to pass it out front, he's got to have someone to pass it to.....so he's going to have to look, which usually means he'll stop moving around as much behind the net to take a better look. This is your oppertunity to take a real quick look yourself. You can do a quick check look before he even starts moving again. Now you know were everyone is, so when he goes to pass, you explode out to the shooter which you should already have a pretty good idea where he's located.
As the level of play goes up, the carrier behind the net won't have to stop to look, and this will comand your full attention. When he passes now, you're going to have to out keeping yourself between the puck and the net......being ready to make the save at any point allong that line.
I hope this made some sense.
Use what you can, throw the rest out........everybodys different.
Good luck!