re: Poker & HOW 2 SPOT A BLUFF
It's all about betting patterns. Look for weird bets: minimum bets, massive overbets, etc. combine that with what you know about the player, combined further with the texture of the flop.
Sometimes one persons mini bet is tptk, sometimes it's a weak continuation bet. Sometimes a massive overbet is someone scared of the two flush cards on the flop trying to protect their hand, sometimes it's ATo that missed and just wants you to fold. Sometimes you can punish a good players continuation bet without any cards at all.... sometimes...
Figuring all this out is part of what makes poker interesting and challenging, and why the answer to questions like "how do you know if it's a bluff?" is always "it depends".
ps. in my experience the mini raise is always a monster (on-line) IF it is a raise of a legitimate bet (2/3 to 3/4 or pot bet). If it's a mini raise of a mini bet or some other smaller bet it's often times a weak attempt "re-steal" without committing or an attempt to just take the lead back in the hand (could also be a real hand depending on how weak/poor the player is).