Instructions
Run a full scan of your system by using a reputable antimalware or antivirus program. Several types of malicious programs can negatively affect your Internet connection by using some of its bandwidth without your consent.
Use the in-game server browser to connect to servers which are close to your current geographical location. The further a server is from you, the longer it takes for data to reach it, therefore increasing your ping. You can access the server browser which in-game by pressing the ESC key and selecting "Change server."
Call Internet service providers in your area and check if they offer faster Internet connections than your current one. "Counter-Strike: Source" requires a fast connection for an optimum game play experience. Consider upgrading to a faster Internet connection if such an option is available to you.