If you are wanting it to be highest quality, then the settings in the attached picture should be what you want. Be warned, it will take a while to trace with these settings.
I am no expert, however. Just play around with the settings till you get something you like, it really depends on what you want it to look like.
EDIT: Also, checking and setting up "resample" will improve the quality of the picture.
Just as it is,
Flip Willie