You could.....go to college.

The education deferment allowed men to defer being drafted as long as they were full time students and "making progress." A lot of men did this--going to college and then grad school. The height of the Vietnam war is generally considered the late sixties. And the war ended in 1975, so an 18 year old in 1968 (Tet Offensive) whose parents could send him to college and grad school would never have seen combat...or indeed probably ever been drafted.

Some people cite this as the origin of grade inflation. Professors who failed a student weren't just upholding the integrity of their class, they were possibly sending a kid to Vietnam. Also, this may be the reason for the physician boom of the 60's (40% more physicians between 1960-1978) and the lawyer boom. This would, combined with the Medicare law, also contribute to the boom in healthcare expenditures and the boom in civil litigation.

Draft deferments: https://www.sss.gov/About/History-And-Records/How-The-Draft-Has-Changed-Since-Vietnam

Grade inflation: http://www.gradeinflation.com

Physician boom: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4191514/