There are many products sold for aquarium use that are specifically intended to remove chlorine. Several brand names include: Prime, AmQuel, AP Tap Water Conditioner, Aquasafe Plus, and many more. These all include Sodium Thiosulfate, which reacts with the chlorine (or the chlorine portion of the chloramine) to form harmless chloride ions. The chlorine is completely and totally removed. This reaction happens instantly. The tap water doesn't need to be mixed with the dechlorinator for any amount of time before adding it to the tank. It's safe to just add the dechlorinator as you add the water into the tank.
There is one potential problem if your water is treated with chloramine. As stated above, the dechlorinator reacts with the chlorine portion of the chloramine. The chlorine is eliminated, leaving the ammonia free in the water. As you hopefully know, ammonia is toxic to fish, even in low levels. So, if you use a simple dechlorinator that only contains sodium thiosulfate, you are solving one problem (chlorine) and creating a new problem (ammonia).
Lucky for us aquarists, our aquarium product companies have a solution. Many of the dechlorinator water conditioners include chemicals to convert the ammonia into harmless ammonium. Look a a few labels. My favorite one, Seachem Prime, states: "Removes chlorine, chloramine, and ammonia". Others that I'm sure handle the ammonia include Tetra "AquaSafe NH/CL Formula", Jungle's "ACE", Kordon's "AmQuel", and Kent's "Professional Ammonia Detox". If the label doesn't specifically mention that it neutralizes ammonia, then don't depend on it to safely treat water containing chloramines.