I won't lie, this is tough. Anyone can throw pieces at the King and force a checkmate. The real dividing line between a regular player and a truly good one is the ability to take small positional trumps and convert them into something more, in my opinion.
A lot of it depends on the ‘time’ of the position. If your opponent has active play, say pieces grouped near your King, then your Rook on the open c-file might not matter. Indeed, as a general rule, activity is more important and more immediate than positional (or material) concerns. That is, if your opponent has loads of weak pawns but very active pieces, more often than not those pieces are more important... at least as long as they remain active
The first step, then, is to neutralize your opponent’s play, so prophylaxis. If you can stop your opponent’s active plans, if he can’t do anything, then your positional advantage will matter more and more. Sometimes you can’t do this, and that’s dynamic equality. Sometimes you can do this to some degree, so mostly stopping his counterplay; you have an advantage, though not necessarily winning. If you can stop all counterplay, then your position approaches strategically winning.
From there, the problem becomes actually winning. You need to convert your advantage into something more concrete, ideally a pawn (or a piece!). You want to invade his position, target the weakest pawns and then promote that extra pawn into a new Queen. That's the general blueprint.
That’s the theory. In practice, it can be difficult. You may have lots of moves that look good, but none that are decisive. Fortunately, it’s much easier to play your position, and in practice your opponents often blunder. I have played many games where I wasn’t sure what to do next when my opponent spontaneously moves a pawn, creates a new weakness and suddenly I’m winning. If you keep up the pressure, they often blunder sooner or later … though I realize that ‘wait for your opponent to implode’ doesn’t help you play the positions any easier.
In general, most positional advantages are best used in the endgame. If your opponent has six pieces, one of them bad, then he might not care. If he has one piece and it is bad, though, then that can be decisive. Simiarly, weak pawns or Bishops versus Knights become bigger advantages the more pieces get exchanged. Improving your endgame play will improve your ability to convert such positions. This also explains why so many people, myself included, struggle here, because we don’t study the endgame enough.
TL;dr: Limit counterplay ; trade pieces ; invade and look to pressure pawns ; improve your endgame play to improve at these positions.
Once you have a positive imbalance such as a superior minor piece, or a space advantage etc., how do you go from there? Whenever I find myself with such a positive imbalance I always struggle to know what to do next.
My gut says target a weakness, or strive to create one which you can then take advantage of with your positive imbalance (leaving your opponent with more troubles than answers), but that's so vague and half the time I feel I'd lose part of my advantage when attempting them.
So when you find yourself with superior space/minor pieces/files etc., what do you look for/do next?
Thanks