Most people rinse them under tap water and check them for snails or snail eggs (small clumps of clear jellylike blobs on the leaves or stems). You can put them in a bucket of tap water and keep them in that for a few weeks but make sure they get some light. And if you are really concerned you can put them in a bucket of cold water with some bleach. Leave them in that for 1-2 minutes before removing them and rinsing under tap water. Then put them in a bucket of tap water and add 4 times the recommended dose of dechlorinator. Mix it through and leave it for a couple of hours. then rinse them a few more times before putting them in the tank.
