We front-loaded. We were/are maxing our tax-advantaged space, and we had a taxable account.
In-state tuition at our 2 big universities is ~$15k/yr, and room/board/fees is another $15k/yr... right now. $30k/yr! It'll probably double to $60k/yr by the time my kids could attend. We plan to be retired well before, but who knows? And, who knows what aid will look like then?
We liquidated taxable to fund $20k at age 0-1 and another $20k at age 1-2 for $40k total per kid, and received the max state tax deduction for our contributions. My children are 3 & 5 years old right now, and the accounts stand at $59k and $74k, projected to be ~$170k by age 18. Will $42k/yr for 4 years be enough? I have no idea. Originally, my plan was to have $240k/kid for college ($60k/yr x 4 years), with half in 529 and half in taxable, but it ended up more than we could do (at least for now).
Meanwhile, to keep myself from despair, I've decided my backup plan for the kids is dual enrollment/AP credits to shorten the time needed at uni or, after reading through BeyondtheStates.com, GOING ABROAD:
Anglo-American University in Prague, where an entire bachelor's taught in English takes 3 years, costs $25k in tuition for the entire degree (!!!) and the cost of living is less than Memphis. Not 529 eligible, but, if you withdrew the tuition & COL anyway, you'd pay income tax on the earnings portion of the withdrawal at the student's rate, and only incur the 10% penalty on the earnings;
Bocconi Unversity in Milan, which is 529 eligible, a bachelor's taught in English takes 3 years, ~$14k/yr tuition, and COL is like Tampa;
University College Utrecht in the Netherlands, which is 529 eligible, a bachelor's taught in English takes 3-4 years depending on the major, ~$14k/yr tuition, and COL is the same as the college towns in my state;
and honorable mention to Bangor University in Wales, which is also 529 eligible, a bachelor's takes 3 years and a master's takes 1 year!!! They're ~$23k/yr in tuition, and COL is the same as our college towns.
There are some very interesting ways to skin the cat, and if you can't make the budget fit the options, you can make the options fit the budget.