(MONEY Magazine) – If you're shopping for a 529 college savings plan and a broker or adviser hands you what she says is the best product for you, can you be sure it is? As your kids might say, Yeah, well, sorta--actually, maybe not.

• WHAT YOU'LL HEAR Your state's 529 plan, which could give you a nice break on state income taxes, may not be among your broker's wares. And until recently, many brokers were selling out-of-state plans while staying mum about the in-state advantages. A regulatory probe last fall led to a rule change that would require brokers to give you a heads-up. The change is likely to be approved by the Securities and Exchange Commission, and many brokers are already complying.

• WHAT TO DO Problem is, your broker would have to tell you only that tax benefits exist. That's all--she doesn't have to offer a plan that has them or even explain what she's talking about. If she provides details about potential savings or less costly no-load plans, you are working with a trustworthy adviser. Still, do your homework. Get savings tips at cnnmoney.com/529. For state-by-state data, go to savingforcollege.com.