1. Use weapons as their role was intended to be. (ie don't use sniper rifles in close quarters, use assault rifles as direct weapons, use energy swords and gravity hammers in more enclosed maps such as powerhouse and reflection)
2. Get to know the maps well. Know where weapons spawn and know where good sniping spots are.
3. Don't be a noob (running around without any idea of where to go, acting like your unstoppable when you aren't, and be sure to NEVER just go into enemy territory without a good plan)