First of all, you are shaved then scrubbed in the scrotal area.
Next a local anesthetic is instilled in the area of the incision. A
small incision is made on both sides of the scrotum, or one in the
middle, depending on the doctor's preference. A small piece of both
vas deferens, the tubes that carry the sperm, are removed and then
the ends are either clipped or cauterized shut. This essentially
puts up a road block, so to speak, so that the sperm can no longer
make the trip from the testicles to the penis and you become
sterile.