Check out George Tsoukalas' site. It has all you need to know. Just look up 3 posts!
There are a few other sites also around.
Some woods are strong in tension like osage, hickory, locust, yew sapwood and others. Some woods are strong in compression like osage, yew, ipe and others. All woods are stronger in tension than they are in compression. A bow can be built with almost any wood if you design it properly for the wood used. It's up to you to determine which design best fits the tension and compression properties of the wood you choose for the selfbow you plan to build.
If you use a wood that is tension strong but relatively weak in compression like hickory a trapped cross section(trapezoidal cross section)will lesson the tension and increase the compression properties of that bow. There are other tricks but learn to build bows with proper tiller first then expand your horizons with different styles and types of bows.