This will only relate to Windows systems.

The first two are the types of update that most people will consider.

Operating system patches.

I have Windows set to download the patches as they become available and notify me. I then usually install within the next couple of days.

Anti-Virus

This is set to download and install automatically. The Avast software I use checks every 4 hours to see if there are updates available.

But what about the other software that you have installed? You probably have things like Acrobat Reader, Flash Player, Java and a multitude of other applications which also have security issues and updates to resolve them. You may remember to update some of them, but are you sure you got them all? The Secunia website has a Software Inspector that will check your system for software versions and provide updates or links to the application website. The inspector requires Javascript enabled to work.

Even if you think your Windows system is up to date, it might be worth a check, it only takes a minute.