Hello Janman,
If the thing you are scanning is of poor quality you could use Corel Trace to convert it from a bitmap to a vector image.
Be forewarned though, if you have Corel Trace (I'm not sure if it was part of the bundle back in Ver 7), it is not perfect. The version released with Draw 9 was a big improvement on previous versions but it is still often better to manually trace.
To trace anything manually you really need to master the basic drawing abilities of Draw. I'm talking about drawing bezier curves, learning about the different types of nodes, symmetrical nodes, cusp nodes, control handles etc.
If all of this is beyond your ability at this stage your best bet is to either obtain a better quality original to scan (if possible) or try scanning at a higher resolution.
Adjusting the "threshold" when scanning may help. The threshold decides if the pixels will be black or white if you are scanning in 1-bit mode i.e. black/white. The higher you set the threshold the more pixels will be changed to black resulting in less broken lines.
Hope this helps,
Joe