The best method... prevent it from happening in the first place with a filtration system. No I am not talking about a water softener or reverse osmosis machine under the sink, but rather one with a sediment filter & one to filter out other containments in the water, which would require a water test being conducted.
As for removal, the related posts had a good one: http://www.hometalk.com/607726/how-to-remove-a-rust-stain-from-fabric though I am not sure how well that works if the clothes are dried in a dryer - does that set the stain or not
this happened to me once. I called the City and the girl provided me for free with some Red-B-Gone, rust and stain remover. Call yours and see if they have anything to give you.