Heck, just start getting familar with what is offered. I'd go to either Gigabyte or Asus's website, plug in the CPU/socket type and see how each of their boards vary. After getting a feel for what's available from a full-range company and what you like, then go to a site like NewEgg and do the same thing, finding the lists that include the boards you looked at and compare prices and features with other brands.
There is no BEST motherboard - have to decide what you want.