Debby Downer here
If the oven racks are still shiny DON'T LEAVE THEM IN THE OVEN DURING THE SELF CLEAN CYCLE!!! It ruins them. One manufacturer finally figured this out and offered porcelain enameled racks but I don't know how durable they were.
Also, one of the big disappointments we had with self-cleaning ovens is that all the grime on the periphery of the oven, which is almost invisible before, becomes very visible and harder to clean after the heat of the cleaning cycle. You might want to remove as much of it as you can. IHMO, after 20 years, I don't think self-cleaning ovens save you that much work. It would be GREAT if you could use pyrolitic cleaning to remove all the crap that attaches to the racks, but you end up ruining the chrome finish and the racks lose their ability to slide.
I think Frigidaire hit on the best system in the early Sixties when they offered modularized ovens where the bake and broil elements were completely removable and you could slide the oven cavity out where you had the option to clean it outdoors.