Instructions
1
Determine where to put the stairs. You may need to level the ground at the base.

2
Measure from the ground to the bottom of the back door in inches. Subtract 2 inches if the door opens outwards.

3
Divide your measurement by seven. This will tell you the number of steps required to make the correct height. Seven inches is the maximum height of steps allowed under most building codes.

4
Multiply by 11. Eleven inches is the minimum width for stair treads under most codes. This will give you the total projection of the steps from the building.

5
Add the measurement for any extra projection, such as a landing at the top of the stairs.

Read more: How to Design Back Door Steps | eHow.com http://www.ehow.com/how_5883625_design-back-door-steps.html#ixzz1sX8n56wf 

Some videos here that may be helpful http://www.bing.com/videos/search?q=How+to+build+back+door+steps&FORM=BVFD