about as good as it gets as far as free goes. Other things you can do is ensure you don't use admin account as your default account so any virus is stuck in a limited rights environment(and thusly easier for AV to get rid of)
Newer windows versions though do a decent job of this automatically though by prompting for admin access for each thing beyond a certain level of access even on an admin account. If you disabled this, reenable it because it helps a lot for preventing virus's from doing anything important.
User a secure up to date browser, keep OS up to date, regularly scan since nonfree version tend to not automate anything, and don't browse random sites, user popup and ad blockers and noscript plugin if you can.
And keep a backup of data, just in case. There is no 100% catchall on viruses and malware, you just do your best to reach that 99%