Where should an aoe2 player go to learn the aoe3 basics before aoe3de?

I've been playing aoe2hd and aoe2de for a while, and I've seen all the info about aoe3de so im interested in getting it when it comes out. However, I can tell it is a very different game. What's a good place to start to learn the differences in how you develop and balance an economy, and how you train an army?

Thanks.