The Power of the Outpost
I've started reading the 4th edition of IM Silman's How to Reasses your Chess. The first imbalance he covers is the superior minor piece. Two of my recent games featured just this with a superior knight wreaking havoc out of the opening. In one case I was able to take advantage of the great knight in the second case I left myself open.
Here's the first occurence
The outpost in the game above yielded an exchange and a powerful positional advantage that would win the game. Granted playing d6 giving up the e6 square wasn't the primary error playing 8...c5 really made that possible. Now it's my turn to miss the outpost.
Realizing a mistake after a move is made is small comfort when one is forced to play the whole game down. In both these cases the outposts yielded material and a positional advantage that would be hard to overcome for the rest of the game. Of course outposts also work well in the middlegame and endgame but don't overlook those juicy sqaures right in the opening!