Alakazam vs. Azumarill. What do you use, Psychic or Energy Ball? Guide yourself with the following steps:
-First, choose your strongest STAB'd attack with 100% accuracy. For my Alakazam, I choose Psychic, but for a fire-type it could be flamethrower, or heat wave if you're risking the 10% miss chance.
-Multiply your attack's base damage times 1.5, and then divide by 2. (Or, multiply it by .75). My result is 67.5.
-I will NEVER use an attack that has less than 67.5 Base Damage, but it's SE, over Psychic, which is Normal Effective, against an enemy. Thus against Azumarill I'm not using ShockWave since Psychic deals more damage.
But I would use Energy Ball (Base 80), which does deal more damage over Psychic.
-Always take in mind type effectivenes. Perhaps I wouldn't use ShockWave against an Azumarill, but I would use it against a Gyarados.
-Always take in mind defensive stats. If your opponent has more defense than your attack, or more special defense than your special attack, you might want to consider other options.
If you don't know what STAB is, you still haven't grasped the basics of Pokémon fighting. Check the Encyclopedia.