the best advise anyone can give you is be VERY CAREFUL WHEN USING 330'S they bite hard and it hurts /ubbthreads/images/graemlins/frown.gif.
now for the beaver part. dont set the den entrances til last, or you will spook the beaver and wont catch any of them, other then the first one. personally I stay away from the den at all cost. find the feed beds and set the channels going to to them or the holes themselfs. you can also use a castor mound set on the bank and use a 330 with it, all you have to do is: make your castor mound then take to bushy branches and spear them in the bank about a foot above waterlevel, so they hang out in the water, (use dead branches for this) /ubbthreads/images/graemlins/smiliesmack.gif leaving a space big enough for the 330 to sit between, also make sure some of the branches are in the water, then lay a branch the size of your arm over the 330 and in the branches, to make a dive pole, the beaver comeing up to check out the castor mound will dive under the pole and into the 330 /ubbthreads/images/graemlins/grinning-smiley-003.gif.
the important part about niuance trapping beaver is to hit them fast and hard, and don't spook them or you'll never get them /ubbthreads/images/graemlins/smiliesmack.gif
If legal, you can also use snares in the trails coming up the bank where they are cutting trees /ubbthreads/images/graemlins/grinning-smiley-006.gif