Be in right frame of mind:
You should ask yourself about the main purpose behind your decision to take on evil. Whether is it just a heroic effort to register your presence or you actually want to shoulder your responsibility? Be true and honest to yourself as the success of your mission depends on your motive.
What kind of evil you are fighting with:
First of all you should have the complete knowledge about your opponent so that you can beat his move even before it is made. Your competitor can be anyone. It can be a simple school guy who likes to take joy in the pain he causes. It can be a corrupt politician who takes advantage of his authority and subvert law and order to benefit himself.
Start from micro level:
You do not need to strike hard straight away in the beginning rather you should start from micro level. Gain strength with small victories and ultimately this winning streak will lead your opponent to a shameful defeat.
Find his strength:
You must know that from where your villain gets power. What makes him so much strong that he is dominating the whole society? Only then you can employ an effective counterattack strategy.
Look for the weakest link:
The villains always have their hamartia and all you need is to find these flaws and make best out of their weaknesses.
Do not act like your villain:
Remember you are representing good forces so you should act like the evil ones during this fight. Your goal is to eliminate the evil not the villain.
Learn from your villain:
One should not hate villains as they are just like other human beings. The difference is only that they fell prey to the evil forces and bad desires. You may learn from them to fight evil also in the future.