MSDN just published two Visual How-Tos that I created that walk you through building the XML metadata for creating an entity and then a series of related entities. They're pretty simplistic in nature and literally start you with a blank XML file. So, if you are interested in learning some of the very basics of the Business Data Catalog, you should check them out :-)
I'd like to thank the the MSDN team for giving me a crack at creating a few Visual How-To's for their site. If you've ever seen me present, you know that I have a very off-the-cuff style of presenting. My presentations are usually demo heavy and while things usually don't go perfectly, you'll generally be able to leave the presentation knowing what happened and why. I like to think I'm good at presenting.
Having said that, I'm discovering that while I'm definitely made for the stage, film is another beast entirely. All of a sudden all of those little goofs that are perfectly acceptable in a live demo stand out like a sore thumb in a WMV file. Naturally, I'll try to fix them, so I go back and edit just that part of the video but magically my voice turns out louder or the mouse jumps or (because I forgot to hide my task bar) I magically move forward and then backward in time between my edits. It was soooo much harder to get right than presenting. I was quite suprised, so, if you see a visual How-To that you particularly like, be sure to track down the auther and send him/her some Kudo's for their hard work :)