This is just my remedy, it works for me, but I can't promise it will work for others. Keep good water quality, feed foods soaking in garlic and vitamins, and the most important piece, my cleaner wrasse. I have had ich in my system for as long as I have had a SW tank it seems. I am one of those "live with it" types of people and when I start to see Ich outbreaks I know I am not keeping up on maintenance or something happened in the tank to put some parameter out of whack, which in turn causes a little stress on the fish in the tank and Ich starts to take hold.
There are many people that say garlic does nothing, and that may be true, I have no proof one way or the other, but I feel like it is doing good. Also people will claim that cleaner wrasses are not suitable for aquariums, and that they don't eat Ich parasites off of fish, both I disagree with. Most cleaner wrasses are not suitable, but there is one, the Labroides dimidiatus, which I have had over 2 years now without problems, have read many success stories with this one cleaner wrasse in aquariums, AND I see it cleaning Ich off of my Potter's Angel whenever it appears. It also cleans all the fish daily regardless if there is ich or not. With a tank full of wrasses, cleaner shrimp are no longer an option for me.