So how do you study the middlegame?

With all that talk about openings in this forum I was wondering how 

people approach learning the middlegame? 

Is it reading Nimzowitsch my system over and over again 

or Secrets of Modern Chess Strategy by John Watson?

Or just tactics tactics tactics?

I myself find it really hard to study it. When to look for positional 

solutions and when for tactical?

Try Silman. 

The Amateurs Mind, and Reassess Your Chess.

Large print, easy to understand. And he deals with the question you just asked in great detail.

But the first thing I look for in a position is tactics. Can I mate my opponent? Can he mate me?

If the answer to these questions is "No," then I go on to plan B, and crush him positionally.

But Tactics first. Strategy second. Tripling your opponents pawns is no good, if you lose a knight in the process.

 Hmm yes I started a few months ago with those silman books but so far I'm going pretty slow 

over it. What I'm trying to do a lot is looking at good bishop bad bishop trades and 

open/closed positions.

Also doing chess mentor on chess.com! Very much fun. But when I look at tactic trainer here 

and on chesstempo.com sometimes I spot everything but other times my mind just goes blank. 

Strange I got the positional understanding on chess mentor under control but advanced 

tactics I blunder a lot.