Preparation is the key to any succssful mechanical projects & coolant change is no exception. Try to make sure the following are in order:  (1) Buy a new drain cock valve, as most drain cock valves are plastic & can become brittle under long term exposure to heat, you don't want to be stuck with a broken or cracked drain cock once your coolant has been drained, (2) Check the condition of your radiator cap, if the rubber gasket show signs of cracking it is time for a new one, (3) Most importantly, locate the air release valve on your engine block, without opening the air release valve you will not be able to drain the coolant from the engine block. Air release valve's location varies depending on the manfuacture, but I found the easiest way to locate it is trace the upper radiator hose back to the engine block. (4) Turn temperature control to full hot, need to drain coolant out of the heater core as well. (5) Buy the manufacture specified coolant, do not use after market universal coolant to save a few bucks.Once the old coolant is completely drained & you have replaced the radiator cap & drain cock valve as needed, fill the system up with the air release valve in the "open" position.  This way you allow the coolant to push the air out of the engine block to minimize air bubbles getting trapped in it.  Once the coolant starts to seeping out, close the valve (12mm wrench on Acura/Honda). Mount the funnel full of coolant to the top radiator with the correct adaptor, then run the engine at approximately 2000 rpm until the cooling fan kicks in, then just stand back & observe if there's any air bubbles burping thru the funnel.Tip: After turning the car off, leave the funnel attached until the car completely cools down because coolant will contract & consequently will suck more fluid out of the funnel.  I squeezed the radiator hose really hard & fast for a dozen times & that seemed to purge even more air bubbles out of the system.In summary, I replaced coolant for all 3 of my vehicles within the last 2 days: Dodge RAM, Acura RL & Toyota Prius. And thanks to this funnel there're no air bubble trapped in any one of them, which we all know can cause erratic idling as well as over heating.