I've heard it both ways. Is this advice from the NRA sourcebook?
Sorry, no citation to my "shoot downhill not up" comment. It just makes sense to me, so take it with a grain of salt I guess.
I've never had my hands on the NRA Sourcebook but it would be an interesting read. Doing some googling I did find this, which has some interesting range ideas:
http://files.dnr.state.mn.us/destinations/shooting_ranges/outdoor_shooting_best_practices.pdf