I've given instructions below for how I learned to poach a chicken at the restaurant, which is how I now always poach a chicken: place chicken in a pot; cover with cold water; partially cover pot and bring to a boil; turn off the heat; let chicken finish cooking while it cools completely in the liquid. This takes a few hours. If you do this method, it is imperative that you let the chicken cool completely in the liquid before removing it otherwise it won't be cooked. I like to do this at night — I stick the whole, cooled pot in the fridge (it's always a challenge finding space), and then pull the chicken from the bone in the morning. You can, of course, do this first thing in the morning, too. Also, if you are pressed for time, just simmer your chicken until it's done. What I love about the bring-the-water-to-a-boil-and-shut-it-off method is that the chicken never over cooks — it is plump and moist and juicy. I should note that when you begin pulling the chicken from the bone, the meat might look pink, which will make you think it is not cooked, but it is — the red spots/blood vessels (this is a guess?) sometimes spread into the meat giving it a pinkish hue. If you are nervous, just plunge the pulled meat into a pot of boiling water for a second and drain it, but I can almost assure you your chicken will be cooked if you allow it to cool completely in its cooking liquid.