Depends on the tank and the snails.
Snails multiply when there is stuff for them to eat... rotting leaves, fish waste, and especially uneaten food. Without those things, they will not multiply.
Malayan livebearing snails (the long, point ones) are very useful scavengers in tanks with sand because they burrow and aerate the substrate, eating anything organic that they find. Some people find them unsightly, but they don't eat plants or fish, so are completely harmless.
Other snails will eat live plants. That's usually why snails are often considered a pest. Clown loaches, Botia spp., pufferfish, and many cichlids will eat snails. There are snail-killing potions, but I'd recommend against them. A bunch of dead snails in the gravel will do your aquarium no good at all. If you do need to cull the snails, try using a trap of some kind. You can make one yourself (think: lobsterpot) and bait it with catfish food, or else buy one from the shops, such as the JBL LimCollect.
However, unless you really have hundreds of the little blighters, don't worry too much about snails. Some aquarists get really concerned about them, but they do very little harm in unplanted aquarium, and if you make sure they don't get fed (by not overfeeding and siphoning off organic waste) the snail population won't go out of hand.
Cheers,
Neale