Here are some additional things to consider.
1. Clean up temporary files and browsing history. Clearing some of this information can speed up the browser.
2. Clean up extensions. These are little programs that add functionality and also take up processing power. As a rule, only uninstall extensions you personally installed. Some extensions install automatically with the program. Those are usually good to leave alone.
3. Clean up (delete) old emails. These accumulate over time and can slow down the email program.
4. Uninstall old, obsolete programs that you no longer use.
5. Use WPA2 (aka WPA-PSK) for wireless security. This will prevent outsiders from stealing band width, and more importantly, using your computer for shady transactions including fraud.
6. Regular defrag has already been mentioned by anort3.