If it's broad information about assets, the general part of this tutorial may apply:
As a specific illustrator tip, make sure to have a layer (and not a group!) per part you want to export.
The more modular you are with the elements, breaking them down in sub-elements, the easier it will be to have total control and flexibility in Spine. But if you're planning to have many skins this could turn against you when you'll need to add a new skin or realign each piece of an alternate pose.
I hope these resources may answer, but if you have anything specific you're in doubt about let me know (:
