Never use shading in a newspaper cartoon. ever.
Keep your backgrounds nice & simple.
Newspapers tend to go for a 200 DPI.... anything else and the picture kind of gets fuzzy. Those people are too lazy to just open up Irfanview and do it themselves.
Draw your own word bubbles. It gives it class & character.
NEVER draw things (like the airplane swoosh) on the computer. Ever.
Thicken your lines or put a slight border around the characters.
Don't try to look tooo professional.... its just a newspaper cartoon that everyone will see.
Use alot of contrasting colors to emphasize your point. Change the orange&red shirts to green&purple or whatnot.
The gradiant effect must be reaaaaaally light to use.... check any Pearls Before Swine strip to see how it looks professionally.
What you'll have to do is create a combination of bold lettering and even spacing.... Impact is so close that the letters will bleed together, and Times New Roman looks like a retard wrote it. Use Comic or Letter-o-matic!.
Here's a cartoon I put into the school newspaper.
http://profound.keenspace.com/images/whstoon2.jpg
Notice how there are only 3 colors (Black, white, and grey), yet it still has character. The borders are shoddilly done, and some of the people look out of place. I also focused on pen techniques rather than computer editing. Notice the cross hatching in the corner and some of the dark sharpie shading. This stuff really impresses people, as they have no idea what to look at first, and confusion is interpreted as genius.
Here's some of my own cartoons that I've submitted to the paper. Theyve been resized to death, but look nice when they're finished. What you really have to do is throw in a random cartoon, see how it looks, and go from there.
http://profound.keenspace.com/newssun.html
Anyway, that's all I have to say. I love your cartoon and your style, and it'd be super-rad to see a Keen-collection of 'em.
-chris 'c'