Re: Hikitsuchi Bo Staff
I train at a dojo with a dojo-cho who trained Hikitsuchi shihan; we do a lot of 'bo' work, but rather than having a set length we guage the staff by the person weilding it. An appropriate length is somewhere between armpit and chin height; the width should be what fits your grip comfortably, but a relatively thin staff will be weaker and a relatively thicker staff will be harder to swing.
If you're looking to get a new staff, wood is a fairly important consideration. Hickory is good if you're going to be banging around; oak is good if you're more interested in studying the movement of the staff; purpleheart, if you can afford it, is pretty good for most uses. There's someone registered here (sorry, I can't remember your name) who knows a lot about woods - also look up the woods page on Kingfisher woodworks.