I've chosen to turn signatures off, but if OldMan47 is linking to the Skeptical Aquarist's page on ich:
http
/www.skepticalaquarist.com/docs/health/ich.shtml then I completely second the recommendation.
If not, then I highly, highly, highly suggest reading through the information in Skeptical's page. He cites some of the best research available in how to treat ich, and addresses many of the myths and misconceptions that exist about ich today (like, there is zero scientific evidence for a dormant stage of ich)
By far, the most important advice is to treat for a long time after all symptoms disappear. You want to be sure to 100% eradicate the population of ich, and that can only be reasonably assured by treating with medication for a good 7 to 10 days (at tropical temperatures) after all symptoms disappear -- all spots and all flicking/scratching behavior by the fish.
Then, once you've dealt with the problem, the next big thing it to ensure it doesn't get back into your tank by quarantining everything that goes into your tank. Any new plants, any new snail, and definitely any new fish. For something like 6 weeks. Once you've killed all the ich, it only gets back into your tank if you reintroduce it, usually on a carrier fish. Another ich myth/misconception is that "ich is in all water" -- also addressed by Skeptical in the link above. Really, I cannoy say enough about that webpage, it is by and far the most accurate collection of ich information I have ever seen on the Internet.