Firstly, update malware definitions on your anti-malware software. Download and install at least two from a well respected source. Look for rootkits, trojans and key loggers. If you do any shopping over the internet, key loggers can sit hidden on your computer and record key presses. They can bypass any security on the store's end.

If you use Linux (and Apple), harden your system.

Malicious computer crime is now bigger then the drug trade. Its not the kid with the computer in basement you have to worry about; its organized crime who have rings of hackers working for them and state sponsored labs.