"Find one of those charts that list all the types and matches them against each other, and learn it by heart. Knowing what your pokemon are strong and weak against can really make or break your battles. Especially for pokemon with multiple types, cause sometimes they'll have one type that compensates for another, so if you based your strategy all around exploiting that one weakness that suddenly isnt there, you'll be fucked. And weaknesses stack too, so don't get caught short."