My suggestions:
Keep the AV always resident and supplement it with occasional scans with MalwareBytes and / or Super AntiSpyware. Also install SpywareBlaster and update it weekly. More important than anything, however, is smart computing. Don't visit or download anything from questionable websites, don't open email attachments unless you are 100% certain you know what they are, don't click on links in emails unless you are certain you know what they are, etc.