A calling station is a player whose main mistake is that he does not fold. Against him bluffs lose their fold equity, so you stop bluffing, value bet wider and bigger, and wait for a hand to charge him with.
A calling station removes your bluffs — the fold equity a bluff needs does not exist — and widens your value range: hands that would check against a good player become bets, because he calls with third pair and ace-high. Second pair can bet the river for value, and strong hands should size up, because he pays the same range either way. Trying to bluff him ‘because he has to fold sometime’ is the classic mistake; he does not, and that is the read.
The read has to be real. A balanced strategy is built so that it cannot be exploited; deviating from it is only right when you have seen a clear mistake over several hands, not one showdown, and the deviation aims at that mistake and nothing else. The opposite player types call for mirror-image adjustments: against a nit who folds too much, bluff more and pay off less; against a player who bluffs too much, check medium hands to him and call wider. Without a read, play the baseline.
Worked example
FAQ
How do you beat a calling station?
Stop bluffing and value bet more hands for bigger sizes. He pays off with weak pairs and ace-high, so hands like second pair become value bets, and your strong hands should bet as big as he will call.
How do you know someone is a calling station?
From repeated evidence: he calls down with weak hands across several hands and rarely folds to bets. One loose call is not a read; without real evidence, the baseline strategy is your best guess.