Notebookreview has published a guide on notebook memory.
But choosing how much you want in a new notebook may be difficult enough, and the terms "DDR" and "DDR2" could very well mean next to nothing to you. This guide is here to help clarify that.
Upgrading RAM can be an equally difficult task, and you don't want to be the pesky customer at your local retail store that says, "I need more RAM" but doesn't know what kind to get. Knowing the internals of your computer is always important, but with RAM it becomes especially so. This guide will also help to clear this up for you.