good advice for the trunks, but what about the branches?
The branches should be marked with a black marker, if possible, as to the TOP.  Branch wood makes the best bows, and the top of the branches make the best backs.   I have seen yew trees with arm-thick branches 20 feet long, practically free of knots.   Goldmine of perfect bow wood.   For branch wood, cut it into the largest useable sections you can.  I usually cut all my staves overlength, and don't bother sealing the back.   When time comes to start carving, i locate the center of the grip, measure out the bow from there, and cut off any checking in the process.
May i ask you, if you have 3 yew trees on your property, just cut one?  Or take the branches?  It's great wood, but a rare tree.  The branches are the best part anyway.  Not to rain on your parade, just saying.  
good luck!