On the list of things we enjoy doing, we'd put ironing somewhere at the bottom of the list, inbetween scrubbing toilets and watching repeats of Mama's Family. Still even further below on that to-do list is actually cleaning our clothes iron. We just inspected our iron's sole plate, and found there was a noticeable build-up of cooked on spray starch, which was impeding smooth movement.
We initially tried using a magic sponge on the bottom, which resulted in a slightly cleaner iron bottom than before, but with noticeable residue remaining despite our gumption to remove the build-up. So we resorted to a household concoction of baking soda and a little water, forming a thick paste, which we then applied to the iron using the magic sponge. With a bit of patience and elbow grease, we got almost 100% of the residue off the iron bottom. Just be sure to avoid clogging the holes on the bottom of the iron (oops, we didn't realize till afterward of our misstep).
The best thing to use is oven cleaner - just heat up the iron for a minute and then spray on the Easy-off or Brillo Oven cleaner - it wipes right off. To keep it from happening again in the future always use a paper towel between the clothes and the iron - also i've seen very thin cloth sold at Target for this use.
If you get mineral deposits in the steam holes, fill the water chamber with 1/3 cup water and 1/3 cup white vinegar. Let the iron steam for a few minutes and the mineral deposits will come out through the holes. It will stink to high heaven but it does the job.
I don't think our iron would be in such bad shape if my husband would use our filtered water instead of the tap water in the iron. However, I have to choose my battles, and I'm just glad he leaves the toilet seat down.
I've always used a piece of wax paper & table salt - turn the iron on, put the salt on top of the wax paper & run the warm iron over it. Works like a charm ...