You leave the country and then change your citizenship. That's the only way to completely avoid it. But then you have to contend with draft laws of the new country.
Another option is to volunteer before you are drafted. That way you get to pick your job.
What happens in most cases is that they do dodge the draft, they report for the draft and then are medically disqualified, but they still report. That is no dodging the draft though, that is just being determined to be unfit for service.
In general, nobody can give you a real answer to this because each draft is different depending on the needs of the situation against the available population. If the need was bad enough, they would draft women. If the need was like Vietnam, there were a lot of disqualification because the need compared against the population was small. In World War II, the need was great compared to the population, so there were not a lot of disqualifications.