Never built a bow but the idea sounds really cool.  I'm handy and mechanically inclined and happen to own hundreds of black locust trees across my property, along with a ton of hickory too.  I found many with very straight and seemingly twist free trunks..

We cut a few cords every year as it makes great firewood.

What do I need to know/do to get some nice bow staves?

Seal the ends with, wood glue, Paint, shellac or something similar when you cut it. Take the bark off as soon as you can and seal the back.

Split them to help them dry faster. I am not sure if you should cut Black locust in the winter or spring. Hickory is cut in the spring as it begins to bud so the bark peels off.

Others will chime in I am sure.

Kelly's right. I seal with spray shellac. It's quick and no where near as messy as glue.

Cut it and split the log in half, seal the ends and put it in the dry for a few weeks then reduce it to staves. Remove the bark and sapwood and seal the back. You can reduce the staves to floor tiller stage for faster drying.
I build locust bow to whitewood dimensions because of its tendency to fret. Locust accepts heat treating very well.