I let my CFI expire back in 02' while working for a regional, thought I'd never need it again. This past summer I realized I would need to get it reinstated. I've been flying wide-body International for the last 6 years and haven't flown a small plane in 7+ years.
I got with the local FSDO and got hooked up with an FAA inspector who would give me an oral and checkride. A date was set, with a Cessna 172sp rented on my dime.
I got with a local instructor at the airport and flew 3 hours of dual with him practicing all the maneuvers and such.
Checkride day came, 4 hours of oral all on initial/private stuff, then 2.1 hours of flight time in the 172sp, had to instruct soft field takeoff,chandelle, turns around a point, stalls, slow flight, steep turns, power on stalls, short field landing, soft field landing, and balked landing (which actually was my fault as I was fast in the flare and floated and called a go-around).
Overall, it was tough to get back into the instructor mindset, and flying the Cessna was unusual as well. I flared 30 feet high constantly as thats what I'm used to seeing when flying the DC-10. It was also a lot of home studying ahead of time as I had forgotten a lot of the basic stuff. There is a great deal of info online, but I did buy an FAR/AIMS and studied the hell out of that. The FAA FSDO will also supply you with a lot of material if you ask, especially Advisory Circulars which have lots of info. In the end I made it work and the FAA was happy and reinstated my CFI.
I will never, ever, ever let my CFI expire again!!!!