If you have Photoshop, you can select the area you want to trace by masking or using the wand, whatever suits you best. Then in the paths menu select make a work path, you can use .5 - 2.0 for the tolerance, the higher the tolerance the smoother it will be but it loses the path a bit. Then in the paths menu save path. Go to file export, paths to Illustrator. Save it. Open it in Illustrator, it's going to only be the paths so do a select all and you'll see the outline, select a fill or stroke color. It's usually not pretty unless you had a really nice scan or sketch, but it gives you something you can smooth, delete and add points to and work with.