If you suspect you might have very smart children (as I did...I mean, that's obvious), then it is NOT a good idea to start a 529 plan or do ANY saving for college.
The reason is that there are about 60 elite colleges in the United States that give OUTRAGEOUS financial aid based on need. Oh...you also can't make more than about $150,000 per year before the financial aid drops significantly. I know that everyone here makes a million dollars a year, but if you happen to have a more normal household income, this advice is for you.
All of the Ivies plus Stanford and many others will give your kid a full ride if you have household income under about $80,000. If you are at about $130,000, your kid will still get full tuition (that was at about $125,000 when my kids were going to college).
What kills that aid is if you have savings of any kind outside of retirement plans, so you need to have NOTHING in a savings account, checking account (beyond basic amounts to pay bills), etc. For people who like to save or have a big cushion of cash available, this is a tough thing to do, but for full benefit of those more elite colleges that do this, it is well worth it.
My oldest went to an elite college that gave her full tuition all 4 years based on our household income and no savings during that time (outside of retirement accounts). Leading up to her going to college, we had to get rid of some cash reserves. In the couple years before she went, we paid cash for some home improvements and bought a car with cash.
If you make much more than $150,000 per year household income, then a 529 plan might be for you.