In my experience, Yew is about the easiest wood in the world to season. Strunk, Welch, myself, and others who live in damp climates don't even seal it most of the time. Unhealthy Yew will check regardless of what you do and healthy Yew probably wont. To be safe: release the tension in the wood by reducing it to staves and billets, or at least halves and quarters. Leave the bark on or peal it off and coat the sapwood with shelack.
J. D. Duff