Well, I like to draw stuff, a lot!! Geeky and not so geeky things alike...(I also make t-shirts)
Anyways, I'll post some pics, tell me what you think about them, and feel free to post your own!!
MadWorld ad I made up, made in Flash & Photoshop, took me 2 hours.
Sorry for the delay, I'll try to explain my workflow, and give some tips. (keep in mind I'm no pro, these are just the things I normally do)
I'm currently using an HP Pavillion tx2000 as a tablet, it lags a bit in Photoshop but it's generally fine. I also have a small Wacom tablet.
I use PS CS3 for sketching and coloring when I'm going for a more traditional look, although you can do almost anything with it. I also use Flash when I need more accurate results or if I need vector art for printing.
I mostly use the standard brushes in Photoshop, but have made some of my own, the wall texture for example. Low opacity, soft brushes give you a wider range of tones, and easier color blending, whilst hard edge brushes are harder to smudge and will give you squiggly lines if your pulse is not that of a dead person or a zombie, that's why I use Flash for the final lineart when required.
Try to stay away from the lighten/darken tool and use layer blending/transparency instead.
The smudge tool is my best friend, with some patience and a soft brush, 35% pressure, you can make wonders.
Also, practice drawing in real paper first, painting also helps a lot, be patient, watch lots of cartoons, read comics, research and observe whatever you can, and most importantly, HAVE FUN!!