An awesome audiophile I know is looking to learn digital DJing with timecoded vinyl.  I start quoting :)

"The software is less important. I would like to learn Serato, but it costs money. So I have been using Virtual DJ.

What I want to learn:

1) Mixing technique and theory  <----This is the big one
2) The structure of a set, how to pick the music and organize it
3) how to map and use midi controllers to utilize cues, loops, samples and effects in the software
4) beatmatching and scratching

I can already do some rough beatmatching with the vinyls, so making one song flow into the next I get. What I really want to know is how to organize songs and play them in interesting and fun ways. That's where the whole mixing theory comes in. I want to know a good DJs thought process while they are playing a set. If possible I'd love to stand behind them while they mix so I can see what they are doing during a performance"