If you don't want to mess with your registry, and you probably don't if you're unfamiliar with it, just go to your services through Computer/Manage/Services and disable the Google Update services. In my case, there are three of them (I have three Google products).
You can also prevent them from starting by using MSCONFIG (or any similar 3rd party program which performs the same function). These will change the registry values for you. If you mess up the registry you can put a world of hurt on your system. If you decide to do it that way, be sure and back up the registry first, or set a restore point.
These comments are for Windows. Mac and Linux users no doubt need different information.