<p>I'm writing a small application in VB.NET and I would like some of the classes to be able to write themselves out to XML to serve as a "save" feature.  I have seen XSD files used to generate VB classes that can serialize themselves into and out of XML very easily.  How would I do this if I do have any pre-existing XML format that I need to conform to as I'm just creating the classes myself?</p>

Since you asked about making it 'easy', then there are three rules to follow that will help keeps things very simple:
Only use property types that are serializable
Don't use collections or arrays as properties that need to be serialized
Don't have properties with "bad" side-effects.  By 'bad', I mostly mean two public properties that are backed by the same underlying private field.
Note that if you break these rules you can probably still serialize your class, but it's likely to be a lot more work.
For item #2, a quick fix is using a datatable or dataset, since those are serializable.