Your opponent's call (OTF) can mean one of the following:
1. He has a better hand than yours, but he calls, not raises, to trap you later in the hand;
2. He has a pair weaker than yours, but isn't sure if you have anything at all;
3. As there are (for example) two
hearts on the board, he may have a draw of
hearts;
4. He has nothing but decides to float: planning to steal the pot with a bluff later.
It's pretty nasty to being traped; it happens to me very often; Sometimes I see that I have missed the flop very badly and at the same time my opponent calls my bluffs, if I am in good shape I realize that I am beat and stop bluffing brutally.
When my opponent thinks I'm bluffing, then poker looks very easy, easy chips. He continues to call with the weaker hand and I push full throttle…
When there is a draw on the board and my opponent is connected to that draw, I
make it not very easy for him to continue; sometimes he misses; sometimes he gives up; sometimes it hits.
And when he floats & later (
if) i decide to make a value bet on the river, I often ask myself;
if he jams the river, whether i will be able to call that jam…
(So, for the development of these
maneuvers is also relevant; opponent, type of game, etc.)