There are two ways to do this sort of job.

1. The 'purist' way is to trace by hand.
2. The second way is automatic tracing, done by a bitmap tracer, and many programs have this function, eg xara xtreme, inkscape, illustrator, corel draw.
I used the one in inkscape [http://www.inkscape.org/] - my preference.
You still need to learn how they work of course.

Being able to trace by hand is a very useful skill in terms of vector drawing.
Also not all images lend themselves to accurate/useful bimap tracing.
Hand tracing is also the best means of extracting part of an image, and frequently the only method that really works.

I'm assuming you have xara xtreme and a good tutorial on bitmap tracing should you be interested is here:
http://www.xaraxone.com/guest/guest53/3.html