Weak points?

Much has been made of best responses during openings and such. However, what do you look for as weaknesses in your opponent's moves/positions? How do you assess your opponent's ability as you progress through the game, aside from rating?

My style of play usually values the pieces:

N=3 pawns

B=1.75 pawns

R=2.5 pawns

Q=6 pawns

P= 1 pawn

If my opponent is unable to value the pieces correctly and makes the wrong trade, I usually see it as a mistake.

So I assess my opponent's skill by seeing if they can value the pieces right (and therefore make the right trades) as the position changes.

Tactics aside, you can easily see positional errors from your opponents such as bad pawn structures (doubled pawns, backward pawns), bad trades (knight for a bishop in a closed position), bad placing of pieces (rooks and bishops targeting solid pawn structures, obstructed fianchettoed bishops, knights on the edge of the board) and so on.

I have seen players rated around 1900 to make positional mistakes that a 1200-1300 player wouldn't make (playing Ng5 against a very safe king, for instance), so rating is just an approximation of an arithmetic mean of your opponent's strength, not the exact value of it.

I too am on the lookout for any possible ways to exploit positional errors and improve my pawn strucure. I am not good at very deep tactics.