This video shows how to manually trace a bitmap using the line tools.
In the video, the initial outline is draw with the 
pen tool. You can achieve the same result with the connected line tool 
.
When zoomed in on a shape if some points are very close together, it can be difficult to click on the point or line that you want. However, you can increases the precision of the selection by holding down the CTRL key in Windows or the CMD key on a Mac.