When you see a strange position, the number one rule is not to panic. Just try to use logic to bring the game to calmer waters. Your position is most likely fine, but the reasons may be totally different than what you are used to. Once you have calmed yourself down, three important things to keep in mind are:
1. Controlling the center,
2. Developing your pieces, and
3. Discovering your opponent's plan.
You should notice that these three principles are things that you have probably seen before. Nevertheless, it can be difficult to see how these ideas can be used when you are in muddy waters. No matter how imaginative and unusual the opponent's plan is, these rules will hold up. They have held for over a hundred years and will continue to govern play for the future because they will win over other strategies. The following game is an example of how to react to an unfamiliar situation:
That game made white's plan look quite silly, yet it was actually quite difficult to Black's position. The most important thing to help me get through this jungle was keeping my cool. Had I played a couple nervous moves around when I played f5, I would have surely been under heavy fire from my opponent's entire army, and I might have been quickly checkmated. The second key to my success was discovering my opponent's plan. I needed to see that my opponent was planning a large scale kingside attack to play a move which is so surprising when seen at a glance. However, it captures what the position demands of me: limit my opponent's piece activity. Once I did this, I was able to spend every free move I had to try to control the center with d6 and e5 and develop my pieces through Nc6, Be6, and Re8. Once I was able to mobilize my army, it was obvious that the classical principles would prove to be correct once again and that I was going to win the game. If you can calmly search for what the opponent is trying to do and focus on development and the center, you will win against any unusual strategies.
Good Luck!
David Adelberg