Is it a planted tank or non-planted. Depending on the set-up, what you need to do is different.
If it's planted, the best way I have found, is to put the fish in buckets with air stones. Pull all of the plants out, and PP them, or wash them in a mild bleach solution (to kill eggs and manually remove any snails you see on the plants.) Then you empty ALL of the substrate, and start with fresh, new substrate and re-plant the plants.
If it's not a planted tank, things are much easier! Manual removal, and limiting the amount you feed (not over-feeding AT ALL, and even underfeeding just enough to sustain your fish.) Also, you can get some cute little yoyo loaches, they school together and are very good snail eaters, stay small, unlike clowns!
I recommend not starving them if you have plants, because they WILL eat your plants til they are D-E-D~>Dead! I had this problem with ramshorns, almost all of my plants were eaten to death because I "limited food" so they WILL eat whatever is available. If you don't provide extra food for them to eat, they will turn to your plants, they won't starve themselves.
You could also get yoyo loaches in a planted tank as well. They like playing in the leaves.