Ruth....I know about the distilled water trick but that would fly over like a lead balloon with my hubby if I added that to my grocery list every week! LOL
Here is what I have learned to do.....I use a small plastic watering can (an empty milk jug would work just as well) and leave the water sit overnight and it has helped alot! I was told once that leaving it sit is better for my houseplants so I just assume it would be better for my iron as well.....I haven't noticed it spitting the gunk out near as much since I've been doing this.
I also use vinegar to clean the coffee pot...works pretty good!