I live in Washington, where there is no state income tax to get credited.
There used to be a blog article I liked on the best 529's, but the author got a job with a financial company, and had to take the blog down. Anyways... I'll summarize.
If you get a benefit on your state taxes from investing in your own state's 529, consider that. Though it's not a slam dunk. Sometimes you have to pay back the benefits under certain circumstances. Other times the excessive fees (due to captive audience) reduce or exceed the tax benefits.
If you don't get any benefit on your taxes, or if it's not worth it: you should invest in the lowest cost plan you can find. This will be one of the plans run by either Vanguard or Fidelity. There are something like half a dozen for each. Utah is, I believe, one of the better Vanguard plans open to out of state investors. Personally I opened my daughters in Massachusetts' plan, since I already had accounts at Fidelity, who runs it.
Yes, first see if you can get a tax deduction/credit, if not some that have been mentioned have been Utah, Virginia
There are a number of articles about 529, here is another with advice by statehttp://www.kiplinger.com/features/archi ... plans.html