How do you set up tactics?

I've been solving chess puzzles for a few years, but it's not often that I find such great opportunities in an actual game. I keep waiting for a tactic-worthy position to pop out of no where, but it never does. So how do you actually force a tactic in a real game? 

You don't.

You use tactics to limit your opponent's options (He can't go there because that gives me a fork), or threaten tactics to force him to defend them. Sometimes your position gets good enough that he can't defend all the different threats, and then you -do- get to force a tactic, but the vast majority of the time, that's after you're already winning.

The answer you're looking for though lies in positional play. A good chess position means that tactics that arise are more likely to favor you. Look into positional play, maybe via "The Amateur's Mind" or another middlegame book, and that'll help you put your pieces on squares where they're more likely to be available for tactics.

You don't force it as such, but you do build up pressure. A typical example is ''something with Rc8-Bg7-Nf6, and maybe a queen somewhere. Set this up and chances increases there is ''something'' with X takes b2 or c3 or Nf6-e4. 

You probably also know the typical structures with Bd3/Qc2 (or the other way around) Ng5 and maybe some rook on an open file. If you see that, a rook sac or a sac on h7 or f6 somewhere gets more likely.

By the way a lot of tactics are not set up. They can just fall out of the air when you are active and the opponent makes a mistake.