I normally try to prevent my opponent from castling if possible, by forcing their king to move or keeping an attacking piece on a diagonal or file.
I tend to make this a priority, giving up the opportunity to capture a pawn or pursue a different strategy early on.
Does this make sense? Would I be better off capturing a pawn if I can? Is preventing castling something that should be given priority, or is it more of an afterthought?
Can you try answering why are you trying to prevent your opponent from castling?
When you think about this more - you realize that castling prevention is just a tactical weapon, nothing more. Of course you can win a game if you are good at tactics, if your opponent makes mistakes, but, to quote Alekhine:
"It took me many years to get rid of the bias that I can win in any position, even in a bad one, using some amazing combination".
The need for playing to prevent your opponent from castling is dictated by the position on the board. Of course it makes sense to follow this plan if you achieved some development advantage in the beginning of the game, your pieces are more active and you have good chances to start a massive attack against the enemy king that's trapped in the middle. Of course, sacrificing a pawn (or even more pieces) in this case is justified, since your positional advantage will compensate that.
What if you can't prevent your opponent from doing multiple exchanges after you sacrificed a pawn? Losing many active pieces (due to exchanges) will reduce your attacking potential. And you will have to play an endgame without a pawn. If your opponent is better than you at endgame - he will force those exchanges with the endgame in mind - entering it in a better (or even won) position. Since he will have at least two advantages over you:
This is very important to consider, since often even a single exchange (of queens) serves as green light to endgame.
Capturing an extra pawn represents a clear advantage. If I had the opportunity to do this, I'd do it before almost anything else.
Preventing someone from castling is an advantage, but only all other things being equal. If you can do this in the natural course of play, fine.
But if you go out of your way to do this, you may incur a disadvantage greater than the other player's lost castling right. For instance, in the French Defense, White may play Qg4, forcing ...Kf8. But this exposes the Q on g4 to attack by Nh6 (or Nf6), and may represent the greater disadvantage. Against a Qg4, the Black K is actually better placed on f8 than on g8 (where the pawn in front of it would be pinned).
I suggest in the opening if you want to keep your opponent from castling, try bishops because they are easily brought out in the opening and don't need to get to close to the wall of pawns unlike knights, but if you want to deal with it quick, a sacrifice won't hurt or you could try the Evan's Gambit, which involves stopping your opponent from castling while stopping the king from capturing any pieces.
