I don't know how experienced you are as a bowyer, but if you haven't already made some good bows from other woods I would hold off using the yew for now. If you have plenty of experience making bows but just not heat bending, then by all means try the yew. Its best to learn basic bowyery on less valuable wood.
I'm guessing the staves are dry, I would then rough one out to floor tillered dimensions, with slightly wide tips, keeping the sides and belly flat and square so you have surfaces that a clamp will hold on to. I would then get a heat gun, they aren't too expensive(a lot less than a good yew stave), and use cooking oil to make sure the wood doesn't scorch or crack.
Whilst steaming and boiling will work with dry wood(especially air dried yew), its not a good idea to reintroduce a lot of moisture into already dry wood in the working area of the limb. Boiling and steaming are fine(best options) if you want to recurve the tips or bend a stiff non working handle.
I would also use a Gary Davis type bow form which allows you to put in a reflex and take out side bends simultaneously.Gary has a dvd available, if you do a google search. Yes its a lot of effort, but it gives you maximum control over the process and will deliver the results you want.
Good luck.
Hamish.