BroadwayBuying tickets online to a concert or sporting event? To avoid problems, pay attention to:

Brokers. Before buying tickets from an independent online broker, check http://www.natb.org/find to see whether it’s a member of the National Association of Ticket Brokers. Members agree to adhere to ethical standards. If you feel you’ve been cheated by a broker on the group’s roster, you can file a complaint through the association.

Pickup requirements. Some online venues sell “paperless” tickets that require the buyer to personally pick up the tickets at the box office. This helps prevent resellers from scooping up large blocks of seats, but it can cause problems if you are buying the tickets as a gift. Check the rules before you buy.

Event details. Not long ago, an Illinois woman who thought she was placing a bid for tickets to a concert in the Chicago area mistakenly bought tickets to a concert by the same performer in Hershey, Pa. The site said the sale was final and refused to refund her money until a newspaper columnist got involved. Make sure you are buying tickets for the correct event on the correct date.

Guarantees. Some online resellers, including StubHub and Razorgator, guarantee that the tickets you buy through them are valid. They also give refunds if an event is canceled. Classified ad sites such as Craigslist generally do not offer guarantees.

Fees. “The ticket price listed at the start of the purchasing process will likely not be your final price,” warns the Fan Freedom Project, an advocacy group based in Washington. Major sites usually add “convenience” fees or other charges.