By now there are probably a hundred guides for buying the iPad online. Each with their own opinion about which iPad you should buy. Now there's one hundred and one. If you plan on buying an iPad you really only have two choices to make:
They make a 16 GB, 32 GB, and a 64 GB version.
For me the decision was easy. I looked at my iPod Touch and discovered that I have 28.3 GB used of the 64GB available. By the time I load Pages on there and the full volume of all I've written, I'll be creeping up on 32 GB, leaving me with little wiggle room... unless I get the 64 GB version.
What if you don't have an iPod touch to gauge your potential usage?
16 GB - Plenty for the casual user that wants to store Apps, associated data, and a decent sized music library.
32 GB - If you have an iPhoto library, and a few movies you bought on iTunes in addition to everything else, this is probably the size to go for.
64 GB - You are a filthy media junky that wants to store an obscene amount of music, movies, apps, documents, and podcasts.
2. WiFi or WiFi + 3G?
Do you have a smart phone?
Yes - Get a WiFi version.
No - Get a WiFi + 3G version.
Obviously, the few of us that buy one of these silly things will likely get whatever we can afford, but this was basically my thought process.