Kate Beaton has a great question-and-answer session up on her Tumblr (and it's only Part One), covering topics from process to setting up a website to marketing and dealing with criticism. It's a fantastic, informative read from someone who knows what she's talking about, though the most important advice may be her response to a question about finding time to create:

Charles Schulz’s famous quote is something we’ve all heard. “Cartooning will destroy you, it will break your heart.” When you understand what he meant, you also understand why he did it for most of his life all the same.