Sand, sand, and sand some more. When satisfied, mask off the areas where the fret board and the bridge are going to be glued on, and the sound hole:
Rig up some method to hang the thing to dry between coats, and start spraying lacquer. I've had very good results with ordinary Ace Hardware clear aerosol lacquer. Sand after the first two or three coats, then apply a couple top coats. If you don't get a good even gloss (or don't want gloss) then lightly steel wool the final coat for a nice matte finish.
The fret board will age more gracefully if it has an oil finish instead of lacquer. I'm using Minwax "Wood-Sheen" rubbing oil; works great. Oil finish the bridge too. Make sure you mask off the gluing surfaces of both before applying the finish.
Next: Attach the fret board and bridge
If you find any of this helpful I'd certainly appreciate a "tip" :-)