You don't know who's more competent than the next guy until you start asking questions.
I would suggest people start out by asking how long they've been in business, what their background is, and do they have a degree, which isn't required. Have they been in the area for a long time? Are they open all year? Do they stand behind their work?
People often wait until the last minute to get this done and realize they can't do it this year. Another reason they should plan early is so they can notify their employees so they can start deferring their money.