How do I know if a vascular surgeon is a good one?

Difficult Question. Perhaps the easiest thing to do is to make sure the "vascular surgeon" you're seeing is one who is certified by the american board of surgery (abs) specifically in the specialty of vascular surgery. The abs also certifies surgeons in "surgery, " or what many of us call "general surgery." these are not the same as vascular surgery and you should pay attention when seeing someone.
Training, credential. Start with training center, board certifications, where they are working now and for how long. Malpractice records can be useful, though misleading if takes high risk cases. Ask your doctor if he/she would send their mother to this doctor.