There is no best defense vs an offensive tactics and there is no best offence against a defensive tactic.
You'll have to compare your ratings and adjust accordingly. If you see your opponent is very weak inside and you have some decent inside players, you might choose for an inside focus like low post/look inside.
If your opponents got great guards and always plays motion, but you can easily match his offense because you've even got better guards, there's no need to play a 3-2 zone as suggested above.
The effects of the different tactics can be found in the rules/tactics section.