I would say that B/W comics, less is more. Don't go crazy with tons of shading like you would color. It just makes everything mush together. The beautiful thing about Manga is minimal shading, and even minimal backgrounds. There is usually an establishing shot and then everything else is left to the imagination.
Notice how there is only 1 establishing shot.
Minimal use of grays, large areas of pure black and white
I think the hardest thing about going from color to BW is that you sorta have to let go a little bit, when you color you really have to color everything which isn't necessary anymore.
Here is my BW comic: