The majority of 529 plans are issued by the state. Each plan has there own state specific rules concerning the changing of beneficiary. Most do not have any problems changing the beneficiary but first check with your plans specific rules first.
One problem you may have is some states have waiting periods that must occur before you can change beneficiary's. There could also be an age cap that would only allow students up to a certain age to participate.
Changing beneficiary of the 529 plan account has a few more restrictions. According to 529 rules, you are restricted to choosing someone who is a member of the same family as the original beneficiary. Same family members can be confusing to most individuals. Same family members normally includes immediate members, as well as in-laws, first cousins, half-siblings, etc. You can change the beneficiary to be yourself as well.
After you are sure the new beneficiary is eligible the next thing to do is contact your plans supervision and fill out any necessary form work and give them the name of the new beneficiary.
When you change the beneficiary you are under no obligation to notify the previous beneficiary. All you have to do is provide the name, address, date of birth, and social security number of the new beneficiary to the 529 plans administrator. It simple and easy to do.