I use a variation of the method used to farm in Nepal. I find contour lines using a level with two short IKEA kitchen cabinet legs taped to it (fancy, I know). I space my contour lines 4-5 vertical feet apart, which can be quite close linearly in some areas of my property. And I use young evergreen shrubs to plant a double hedge along the contour lines - two rows 18" apart with the shrubs planted 3' apart in each row. In my climate it's important to use evergreens, because we get most of our rain in the winter, so I want something that will actively be pulling water out of the soil at that point.

I've used dwarf box in one spot and azaleas in another, but you'll want to use something that will survive well in your soil and climate. I'm infilling with herbaceous perennials, and I'll be filling the gaps between plants and shrubs with annuals until the perennials and shrubs grow up and fill in the gaps. Planting the hillside is a cross between mountain climbing and contortion, but it's worth it to keep the hillside in place. My neighbors probably think I'm crazy though. :)

Here is a link that might be useful: Contour farming in Nepal