Don't Go It Alone
Drawing comics--especially comics for print, which no one will see for months or years--can be isolating. When I started working on my first longer story, I knew my biggest challenge would be to motivate myself in a vacuum. Here are a few ways I've dealt with the solitude of drawing, and made it a little more social.
1) CONSCRIPT AN AUDIENCE
When I start to draw a book, I recruit several friends (anyone with whom I'm comfortable sharing rough work) and give them access to a special web directory. Every few days I upload new pages into this directory, my audience reads through it, and occasionally I'll get feedback. The important thing is for me to feel like I'm drawing for someone other than myself, like someone is waiting with bated breath for the next chunk of pages. In the absence of an involved comics editor, this system works for me.
2) SHARE YOUR STUDIO
I've shared studio space with my husband since last year, and it's definitely helped increase my productivity. If Mal's cranking out page after page next to me, I'm more likely to get to work, and having someone around to see me slack off helps keep me from donig so. He's also great for feedback if I can't get a panel to work, or if I need someone to photograph me while I pose for reference.
If you don't live with an artist, think about renting studio space and sharing it with another cartoonist, or even an illustrator or fine artist. If you're a full-time cartoonist or freelance this makes sense, because you'll be separating yourself from the distractions of working from home.
3) FIND A COMMUNITY
Without the support of cartoonists I've met on the internet, there is no way I'd be drawing comics today. Get to know the locals! Join Livejournal, an important networking tool, and "friend" everyone you know--plus anyone you admire. This is a great way to get instant feedback on your work, and the site allows you to control who sees what you post, so it's more private than asking for crits on a message board. Join or browse a couple message boards, too; you'll probably run into board members again online, or in person at conventions. Of course, the trick is not to let these sites turn into time-wasters.
If you're more interested in meeting cartoonists in your area, consider joining (or forming) a cartooning group. It may not always be intellectually stimulating, but at least you'll get to meet others who care about the minutiae of pen nibs or the properties of different brands of ink.
4) GO TO CONS
They're expensive, but they're important. In addition to meeting your peers and fans, and getting your work into the hands of publishers, you'll come home inspired, energized and ready to DRAW. Seeing how many other people are toiling away out there, drawing in their bedrooms and on their lunch breaks, scamming copies and screenprinting covers in their basements, makes coming home to another blank page a lot less lonely.
Good luck! :D