Dave,
I wanted something sturdy for stairs in my garage and ended up designing my own. Below is a link to some pictures but with words, this is what I did.
I measured where I wanted the steps to be and then after making the wrong cuts on my first stringer I made a second correct one and a third to match. I had never laid out stringers but there is info out there on how to do it.
I then attached some 4" wide x about 12" long strap style hinges to the new stringers and the ceiling.
I then installed the steps and risers to the two stringers. Since I had limited room for my installation the steps are shallow and tall but workable for what little I do go up and down them.
I then went and bought 4 garage door pulleys, some garage door cable, cable clamps, threaded eye bolts, some sections of angle steel with holes already punched into them, some all thread, and an assortment of nuts, bolts, and nylon locking nuts.
I then installed the threaded eye bolts halfway up on the stringers to where I could attach the garage door cables. I then layed out up in the rafters under the roof sheathing where to put my first set of pulleys. I then took some of the angle steel with the holes in them and located the pulleys there. I then took some more angle steel and made mounts for my second pair of pulleys close to the outside wall of the garage and spaced them so I could hang my counterweights below them.
I had thought of using an old cable garage door opener but was worried about reliability so I decided on a basic counterweight system consisting of stacked bricks held together with all thread.
Once I got the cable attached to the eye bolts in the threads, ran over the first set of pulleys in the rafters and then over the second set close to the wall I temporarily rigged up some stacks of bricks to find out how many were needed to counterbalance the weight of the new attic steps. Once I found the right amount I adjusted how for up on the cable hanging down from the ceiling and where they needed to be attached at. On mine I added a 1x6 to the walls behind the brick counterweights to keep the walls looking nice and not have them rubbing against the drywall.
To secure it in the up position, I added a basic gate catch that has the pin attached to the bottom of the new steps and the catch to the ceiling joists.
To fine tune it, I added a trim molding to the underside of the steps to where when they are in the up position it looks more finished and seals up the gap for better sealing and make the furnace work less.
Something I wanted on my install was a light in that area to where when the steps are in the up position I have light below them in the garage.
Steps in the up position:
http://home-and-garden.webshots.com/photo/2376570230060464735VORWeQ
Steps in the down position:
http://home-and-garden.webshots.com/photo/2177862520060464735VHogTt
Detail of pulleys and cables to counterbalance the stairs:
http://home-and-garden.webshots.com/photo/2954157990060464735PNGMiB
Jim