When I was a little kid I wanted to be a concept artist for D&D (I'm not sure the word concept art existed back then.)
Anyway, I've been recently absorbing the blog of the art director for D&D Jon Schindehette who has the chimeral task of "building the artist community", so his blog is very aimed at advice for people who want to be illustrators, and highlights of illustrators he likes. It's been interesting and informative so far.
Once I finish digesting Mr. Schindehette's I'll move on to Irene Gallo's art director for Tor Books.
Also to be checked out: Ninja Mountain Scroll podcast and blog
And world building podcast (with a not intuitive site for finding the podcast)
and Wip podcast
This post on the artorder blog had a breakdown of the order and timeline for illustrating, which might be a handy benchmark reference