How do I lower my ping in online games?

Hello, so I've been playing online games on my computer for awhile now, games like Team Fortress 2, Counter Strike, Call of Duty, and my ping's always been fine but recently (3-4 months ago) my ping has been awful, peaking at 300 in servers where my ping would usually be 50. I've unplugged the ethernet cords from my modem/router (I obviously don't know too much haha) that didn't seem to do much, then I turned off my firewall because I heard that could do something but it didn't do anything. What more can I do? Thanks for answering. Also, my speed when browsing the internet is really fast so I don't see why there would be a problem.