Ask it. And if the motherboard gets up and dances for you, its good. :lol: Just kidding.
Motherboards from the major companies are all pretty good. They have found that they need to see a quality product in order to sell lots of them, and they need to sell lots of them to stay in business.
Anything from Asus, Asrock, Gigabyte, MSI, and maybe EVGA should be good.
Now if you are looking at a used motherboard, there is no way to tell that its in good running condition without hooking everything up, and turning the system on. I've never been comfortable with buying something I could not see running first.