Back in the day, (I really dislike the expression) everyone who played games on a PC knew how to optimize it to within a nanosecond of it's life.
Today you are lucky if players know what is under their hood.
nVidia and AMD/ATI have all but neutered tweaking gamers.
nVidia wants to load a streaming service - and players wanna know why the game they are playing is lagging?
Or they use WiFi as a connection and wonder - "What is packet loss?"
Okay, here are some basics.
First rule is to minimize what is running in the background.
One of the best ways to learn about programs running on your computer is to go to Black Viper's site.
He teaches you to run services.msc.
Open the run window - windows key + R
What you'll see is a list of ALL the programs that launch on your computer.
Some are .indispensable. He'll let you know.
Some are superfluous garbage, he'll let you know that too.
Some Anti-virus suite have a "game mode" to limit the interference while you're online gaming. Cheaper AV flags any change to an executable as a virus so every update to your favorite game causes your AV to quarantine or delete you game.
Then there is your router.
Have you enabled UPnP?
Many times a game wants to use specific ports UDP or TCP.
Each aspect of you PC is worth examination.
When was the last time you opened the case and cleaned the dust from your CPU heatsink fins? Your GPR heatsink?
Does your power supply allow for a good deal more wattage than you normally consume? Or are you running at the limit?
There are some great programs to monitor your hardware.
HWiNFO64 will show you everything you need to know about your hardware and it's performance after running a game.
If you have any general questions about tweaking your rig, ask away.