What technical specs does one need to know when self-publishing?

I just began collaborating with two illustrators to do a children’s book and a comicbook both with the intention to self-publish as an E-book and/or a print to order book.

Collaborating with artists through the internet and self-publishing are new experiences for me. Any helpful tips on what to watch out for with regards to technical issues would be very much appreciated.

For example, the minimum resolution needed in an image that would result into a decent page when printed.