EXCELLENT advice right there from Bmorv. Read that twice.
Some guys think because it's a laminated bow that they can use any old piece of wood.... especially for the core.... ya know.... maybe it has knots, is warped to the side, or has runout, or a swirly hard spot, or it's cut flat grain and cut through a bunch of growth rings, etc. I won't use that stuff. I'm not saying you can't make a bow out of some of it, there are varying degrees of quality, but the best bows are made with the best materials and I'm done fighting bows because I tried to use something I should have burned.
I've burned a lot of bow wood culling my stash to have good quality wood in the shop, and I understand not everyone has access to it or makes it the priority I do... I'm just saying... use the best you can get your hands on.
On a scale of 1 to 10, I want the backings to be 10's, the cores to be clear 7's or better, and the belly lams to be 9's or 10's.
One wood that I will lower my standards for just a wee bit by comparison is Yew, only because it seems to deal with knots differently than the hardwoods do... and I mean a WEE bit. I'm still very picky.