the only way I have ever eaten a pom or seen it done was to cut a shallow slit from top to bottom, insert two thumbs and pull apart, then dedicate about 45 min to picking the seeds out one at a time. it's good meditation, or something to do in a boring lecture, or while someone else is driving on a road trip.
We were watching Iron Chef America and saw one of the sous chefs split the pomegranet down the middle, then he held it over a bowl and spanked it with a wooden spoon! I tried it at home and, while it did knock out some of the seeds, it didn't get nearly all of them, and it smushed all the ones on the spanky end. Seemed like a good idea, though.
Anyway, the best way I've found is to split it down the middle, then try to keep "peeling" it so that you're coming away with clumps of seeds stuck to the peel. Then you can just sort of rub at them to seperate and remove any little bits of the white pith. Either way, such a large amount of trouble that I almost never buy them.