Hello

I've been wanting to get into digital art after browsing through sites like the Newgrounds art portal and DeviantArt, but whenever I draw something on the computer, all the lines look "wobbly". I'm not sure how to get it to look smoother and more "professional". I'm curious to know what other do to get this effect. Should I invest in a copy of Illustrator or other program? Should I just use a ruler when drawing on the tablet? Or perhaps I just simply need more practice using digital media?
Right now I have a working scanner, a Wacom Intuos 3 drawing tablet, a copy of Photoshop CS3, all running on Windows Vista.
Any tips would be greatly appreciated. Thanks!