Here's a link to a slideshow of the building process for my DIY deck stairs; I had to remove the original stairway last year as part of the residing job I was doing, and since the veranda rim joist had suffered dry rot due to improper original flashing. I used PT 2x12s and 2x6s for the stringers and treads. The biggest problem was the 10° skew the stairs had to take from the veranda to remain on the deck. That threw off the alignment of the treads, forcing me to cut out small divots in each tread where it meets the stringer; a bit tedious, but it worked out in the end. To calculate the runs/rises I used a free online program that worked simply and well.
The two side stringers at the deck end of the stairs land over a 4x8 and 2x6 joist; I added a concrete pier under the 2x6 joist at that point for additional support, although the original stairway lasted for 16 years without it, and the deck itself appears to be in good condition. This is in Japan, by the way, where space is at a premium, so I think the height of the risers (216mm = 8.5") is a bit more than US code would allow, but still not uncomfortable to climb (you should see some of the ladders I've climbed in commercial inns (ryokan) where I've stayed on occasion.
". . . and only the stump, or fishy part of him remained."