When I dry-hop a recipe, I tend to use the following procedure. It nicely prevents any free-floating hop pieces from making it into the final product while giving the most exposure of hops to beer that I can imagine. It all starts with a larger, wider-mouthed carboy. It's an investment I have been happy with. I just can't bring myself to use "open-bucket" fermentation; I need glass with a good seal. The large-necked carboy lets me work my dry-hopping method, and also is good if I want to throw large things into a secondary fermentation.
I fill a sanitized mesh bag with the dry hops and shove it through the neck - the wider mouth makes this possible and makes it possible to remove the bag intact later. I loosely tie the bag shut and leave a long end of free twine with a loop tied in the far end. The extra twine will make it easier to fish the bag out at the end. I rack from the primary into this setup. (Actually, I've also used this setup in the primary with great results - read on.)
Because I'm using a bag rather than letting hops float free, the hops are all pillowed together. The whole bag just floats with about only a quarter of it submerged. So I take a long metal rod and push the bag down so that it's about halfway down to the bottom of the carboy. I don't push it all the way down because I don't want the bag interacting with the sludge.
Then I wedge in the bung and the bung holds down the other end of the rod. This way the bag is stuck submerged. My intention is to get all of the hops exposed to liquid. Also, just in case there were a sudden burst of fermentation (or if I am actually in a primary stage), I don't risk the bag or free floating hops getting pushed all the way up to the neck and choking off gas escape.
The hops are 100% submerged and at depth, the fermenting currents are scrubbing the hops. The product racks out with no hop leaf particles. However there is a beautiful sheen of lupulin drops floating at the top of the carboy. The IPA's I have made with this method are very very fragrant.
After racking to bottle or keg, the bag can be removed without hassle due to the wider mouthed carboy. It helps to fish the bag out with a coat hanger or something - that's what the loop tied in the end was for.