Choosing To Not Register
On a percentage basis, not registering is the most likely way to prevent you from being drafted. The book Chance and Circumstance states that between 250,000 and 2 million males did not register for the draft during the Vietnam War. According to reports from the Selective Service System, forty percent of the men who are required to register for the draft don't register in the sixty-day time period required by law. At least one or two percent still haven't registered by the time they are twenty. At age 26 they are no longer allowed to register. Thus, the number of permanent non-registrants increases daily. There is a known minimum of at least 300,000 people, perhaps a million, who are becoming permanent non-registrants.
If you refuse to register with Selective Service, you'll receive threatening letters, at first politely reminding you to register, then threatening prosecution, finally informing you that your name has been turned over to the Department of Justice for possible prosecution. These sound scary, but they're mostly bluff. No one has been formally charged since 1986.
In the early 1980s, 21 men were indicted for refusal to register: 19 of those 21 were public resisters. Wherever there were trials, the rates of registration actually went down. This resistance halted prosecutions
http://www.duckdaotsu.org/resist.html