They accumulate earnings over time and by the time your child goes to college you will be able to withdraw funds for college TAX FREE.
The best part about 529s is that there are several different options you can choose from, and you aren't limited to the plans sponsored by your state, you can use whichever plan works best for you.
For example, I live in South Carolina and use Utah's Educational Savings Plan because it has no minimum amount to open one up and it has low fees.
Hope this helped. Good luck with your search!
In my opinion, whichever plan or commodity system you use is just supplemental to a very simple thing: go to your bank's online account, set up a regular transfer (monthly in my case, maybe weekly for you depending on when you get your salary in your country/state) to a savings' account in your kid's name with a decent rate, and just watch it grow.
Then adjust to salary fluctuations if needed.
Also, prefer a tax-free savings account.
Been working fine for me for my oldest who's now 4 yo. Started by saving only a little each month and increased as our financial pressure eased up a bit.
For his sister, I already set up a similar thing and I will "equalize" both accounts with additional payments over time (Hmm, actually, maybe that's not fair and they just need to be "equalized" in that they both have the same amount for a given age... but that's another question).
Another option, which I set up for my oldest but not for his sister was a child trust fund with an initial payment. We moved countries and I don't find a plan that I find similarly attractive here, and the other one is locked until 18 yo. But, as with all portfolios, it comes with a risk.
Note that I don't live in the U.S. in the land of crazy college fees. Though I've studied myself in countries where fees were already a drag (and I'm being polite) for various fields (IT and music studies, anyone?), I have to say when I see fees for the big league universities and colleges in the U.S. I am kind of shocked. Doable, but good luck with that and with your loans.
529 is good. Though, I would avoid other kinds of investments in kids names and or setting up accounts that are too complex or difficult to use as college costs will come in may aspects starting application fees and travel expenses when looking for college as well as housing and allowance spending.