There are loads of tuts. on the net on this subject and one of the best you can have a look here: http://blogs.adobe.com/adobeillustra...and-guide.html
If you have PS you can save yourself a lot of time by improving your bit map in this programme. You might look at posterising your bitmap or in increasing the threshold, the levels. All of this type of work will depend on your bitmap content and what part of the bitmap you want to vectorise. Here is another tut explaining what you can do: http://www.vectordiary.com/illustrat...race-tutorial/