Make Good Use of Your Four Moves
Each Pokémon only gets to use four moves in Battle, so you need to make good use of them. I recommend not using two Attacks of the same type, for example, you wouldn’t want to use both Fire Blast and Flamethrower. Unlike when you’re playing through the game, when you’re Battling you don’t need to have Pokémon that know all of the Hidden Machines or HM’s, so using moves like Strength, Cut, or Rock Climb is a wasted move in my opinion.
Also, moves that are the same type as the Pokémon using it get a power up, so always try to use a move that’s the same type as the user, even if it doesn’t hit anything super effective like Normal. Try to fit moves on your Pokémon that can hit your opponent’s Pokémon’s weaknesses super effectively. For example, a Water-type makes great use of the move Ice Beam because it can hit Grass-types super effectively.