Here is how we did it:
First of all, we never started off saving for the $500,000 - $750,000 it is going to cost us. The higher number is if our younger daughter goes to med school. Our first goal was for tuition, books and fees at a solid public school. The next goal was living away from home at a state school. The next goal was graduate school and/or private school. I felt we owed the kids the first one - the others were gravy. For those who will say there is no state school where they live - where you live is a choice. When my oldest was 6, we moved. Our criteria were - job availability, reasonable cost of living, reasonable crime, excellent public schools and a solid 4 year state university within commuting distance.
When I was pregnant the first time, our income was $35K. We started saving $150 a month. Every month. It would take a long time to get to $750,000 at that rate. But - from every raise my husband got, we saved increased our savings by half of what he took home from it. So - if his raise netted him $200 a month - college savings went up $100.
We hit the first goal when my oldest was in the first grade. We hit the second when she was in junior high. The third took us until she was in undergrad.
We started out saving $150 a month. We ended up saving $4000 a month. We are continuing saving that even though we have enough to pay the $750,000. We are going to stash that for travel when my husband retires in a few years.
It comes down to how do you eat an elephant? One bite at a time.