By far the most important step to fighting ich in the tank, is to fix the problems that made the fish succumb to the infection in the first place.
Happy, healthy fish generally don't get ich, even when a sickly tank-mate is spilling ich trophonts into the water by the hundreds. So the first step is to determine why your fish have ich, and remove that stressor. It could be water quality, it could be recent shipping stress, it could be incompatible tankmates, it could be a lot of things.
Fix the root cause and you'll have much more luck with things like Garlic, Selcon, and KickIch that might help your fish recover under good tank conditions.
If you want ideas about what your root stressor might be, it would be helpful to list some tank details, water test parameters, fish in the tank, any recent additions or changes, etc.
Nate