I would run VEW once in a while to see if there is anything odd going on. You can certainly look at Dev Manager but unless you have a good idea what is there you can't really tell when something new is there.
Make sure you are up-to-date with Java and Adobe. Older versions are dangerous and should not be left on your PC. Make sure Windows is up-to-date. Never use P2P programs like uTorrent or Limewire or Frostwire. Be careful when you download something. Always save it then check it with virustotal.com before you try to run it.
Use Firefox or Chrome and make sure you have AdBlockPlus. To really be safer you can use Firefox and get the NoScript add-on. It's a pain to use but it definitely makes it safer.