A calling station is a player who can almost always be counted on to call a bet and who very rarely bets or raises for value himself. This is usually a passive player type. When a calling station starts betting or raising, look out for the monster he's holding.
Strategy against a calling station:
1.-Don't bluff: Bluffing is usually necessary to win some pots in poker, if you're only going to play great hands, oponents will usually fold when you show aggression, However, when you're up against a calling station, Bluffing is one of the worst things you can do, they will call your bluff with almost anything, so don't try bluffing these players unless you want to lose money, However, this does have ONE upside, If a calling station catches you trying to bluff them, then they probably aren't going to fold to you ever again, punish them when you DO have a good hand!
2.-Value bet at every opportunity: A calling station doesn't usually care about the size of a bet, big or small, they'll most likely call, hoping that the turn or the river will improve their hand, that's why, If you do get a good hand, You should avoid slow playing(as the calling station will most likely just check you back) and insted value bet against these guys at every opportunity, just don't go too far, while these guys like to call bets just to see the turn and the river, they usually wont just mindlessly put all of their chips in one pot with absolutely nothing, make reasonably big bet at every street to reel them in.
3.-Respect their aggression: When a calling station starts to bet and raise, consider your hand strength, while it is hard to put a calling station on a specific hand due to their very wide range, If they do start to play back at you, you're probably beat, why else would they break from their passive play of simply calling, wanting to see the turn and the river?, these kinds of players also dont usually bluff a lot, becuase in order to bluff you have to make bets and these kinds of players prefer to call bets rather than make them