In this post, Pioneer Web Design discusses methods for Keeping Windows Running Cleanly Each Day. Security is always job one here. Make it yours also.
This article has been updated as of Feb. 8, 2013 to bring to date some links and add a note about Java.
Please also note: below applies to Windows 7, Windows Vista and Windows XP SP3 users only now. Windows 8 comes with Windows Defender for Windows 8 which is essentially Microsoft Security Essentials. AV protection is included out of the box. That said, you can check with your favorite AV vendor for a version that works with Windows 8 for your edition of Windows 8.