To make a slope seem steeper, plant at the top. To minimize its steepness, plant large shrubs at the bottom.
Consult an engineer before regrading or building on a steep slope.
Safety-related resources on the Web:
Index of Occupational Safety and Health Resources (http://turva.me.tut.fi/~oshweb/)
National Safety Council (http://www.national-safety-council.ie/)
National Institute for Occupational Safety and Health (http://www.cdc.gov/niosh/homepage.html)
Other safety Web sites
Improving Drainage
Rough Grading
Building Retaining Walls