You'll need to terrace a slope of 20-30 degrees. Paths should be flat or gently sloped, and smooth, no pits or mounds. Uneven footing wastes an enormous amount of energy in a garden or farm, and makes injuries more likely.
When we put the beds in at the student garden at the Stanford Community Farm, we ran lines to mark the rows of beds and the paths in between (paths between beds should be 2' wide, larger access paths on the sides should be 3' wide to accommodate wheelbarrows). We made a wooden frame 15' x 3 1/2' out of 2 x 2's, then used it as a template to frame the beds, cutting with a spading shovel along the edges. Beds of this size are about 50 square feet, which makes it easy to calculate organic soil amendments, whose application rates are usually stated as lbs/100 square feet.
Start at the bottom, and cut into the slope to flatten it. Cut in the width of one bed, plus the width of the path on the other side of the bed, and pile the dirt from the path on the bed to make a mound. Beds should be no wider than 3 1/2' (30"). Most people make beds 4' wide, and then have to strain their backs to reach weeds in the middle of the bed; only tall people can do this comfortably, so design the bed width for people of average height.
Make sure you have a flat "staging" area near a road or driveway, to bring in and deposit bulk materials like manure or compost. Have easy access from this area to the rest of the garden. Also, if there's any shade, it's probably a good space for a communal area for grills or a wood-fired pizza oven. Have a space where people can gather and share what they've grown.
Good luck, may your community garden prosper!