Helpful Tips:
1. Make sure the resources on your system are not close to capping: RAM, CPU, Bandwidth etc.
2. Use wired keyboard and mouse. You don't want to mess with batteries or shotty transmission during a game.
3. Don't use too large of a monitor just for the sake of having a huge monitor. Your eyes traveling across that display or even having to turn your head takes a lot of time and those milliseconds count!
4. If you are not using an SSD in your system, you need to. Throw your OS and games on the SSD, you'll be much happier.
5. Always check the keybinds before playing a game. Sometimes they might be optimized for you but don't be afraid to make adjustments to what fits you best.
6. Study the game because you will be playing against gamers who've mastered it. Learn everything you can about the maps, classes, items, skills, etc. AND HAVE FUN!