Lay a long board across the summit of the slope. Measure from that distance to the base of the slope. Plan on a completed 6-inch rise per step, taking into account the thickness of the stone you'll be using, and the base layer, be it sand or cement. Calculate the number of steps you will need to cut into the hill.
Shovel out each rise, allowing for a 12- to 16-inch setback for each step.
Pre-arrange the stones on the ground, grouping them into steps, incorporating different shapes and sizes into each step. Lay out as many groupings as you have steps.
Begin to lay the steps. If you are using a sand base, start at the bottom of the stairs, placing a bed of sand one to two inches thick and laying the stones carefully on top. If you plan to cement the stones in place, begin at the top step. Lay a bed of cement that's not too soupy, and at least three inches thick. Lay the stones on top, and tap into place, using your trowel and checking for level. Allow the mortar to dry completely.
Fill dirt in between each stone for a natural, aged look. Add gravel on either side, to promote drainage. Finish off with plantings.