The best advice I received when I started freelancing ten years ago was "When you're cartooning full time, remember to draw for fun." Well, that, and "Remember to put on pants BEFORE you get in the car." I don't even remember who it was who told it to me but it was at the 2003 Stanley Awards weekend. The point was that no matter how busy you get, no matter how many deadlines you have on the drawing board, always make time every week to draw for yourself. It makes a world of difference to your enjoyment of the work you do- and you see the results in your work.
It's so easy to just bury yourself in your studio-hole and work away on all your deadlines to get them done, but if that's the only time you draw, it'll very quickly become a chore. It'll become work, and you'll start finding excuses not to do it.
My weapon of choice is life drawing; it's a great way to remind your eye to draw what it sees, not what it knows.
Warm-up sketching is important for good work too. Think of it like warming up for a sport or a workout. You need to get your head in the game before you start work. It's about as close to being athletic as I get.
Here's a video of a studio sketch from this week:
More freelancing and pants-wearing tips, click here.