Recently I went through a book on the middle game where a nice explanation was given on material imbalance. I have distilled these down to a few of points which might be useful to readers.
When you give up some material what should be the compensation?
1. Strong attack on opponent’s king: This is well known and don’t need any explanation. Any kind of material sacrifice can be given if you are getting a mating attack.
2. When your pieces are nicely coordinated and on the other hand your opponents are not. Here is the game Spielmann vs. Moller where Spielmann had sacrificed a queen for two minor pieces:
3. If you have a lead in development and can force your opponent king to stay in the centre, you can give up some material. Here is a nice game of Paul Morphy, normally I use this game for explaining use of pin in practice but it applies here too:
4. You get a strong passed pawn or pawns and your opponent can’t create a real blockade. I really enjoyed the following game when I was preparing against the Sicilian in the past. Rauzer sacrificed a piece sacrifice just to play better endgame. A nice explanation is given by Garry Kasparov in his DVD Play the Najdorf using the game Bronstein against Najdorf: