I was gonna say the same thing as Fate. xD
I'm still somewhat of a beginner but in my years of practice I found that if you want to draw good clean lines and circles, just draw lightly and don't press hard. It's ok to lift your drawing tool multiple times while drawing just a line or circle, just make sure that each stroke is evenly connected.
And it helps allot to start out with sketches, don't try to draw a perfect picture in 15 minutes. Just draw a quick sketch and lay out the idea of your drawing so you can keep the image in your head. Know what you want to draw; I always try to picture the drawing on the paper before I start.
I'll try to post some examples, also check out my deviantart page, the link is on my profile. Again, I'm still a beginner myself so don't expect anything professional. xD