how do you drain the gas tank

A syphon pump, although newer cars have a screen in the fuel filler neck, which makes syphoning the fuel impossible. You might have to remove it then drain it, There is no drain plug in any gas tank.

Run the car until the fuel level is near empty and then remove fuel tank.  Pull the fuel pump and screen and drain the rest of the fuel from the tank.  Remove any debrit that you might find in the tank at this time.

if you have never pulled a tank take it to a garage you trust.this is the most dangerus job that can be done on a vehicle.

On that car you can simply run a hose down the filler neck to drain most of the gas out. Once you are about half/ quarter tank you can simply disconnect the fuel filler hose from the tank(the big one among the few) and continue to drain gas out with a hose. once you do that you should be able to drop the tank. It is a little hard push the hose down into the tank and get it back out but this car will let you do it. I have personally done this with my car and a couple others. The simple way is to run the car down empty but im sure you already thought of that:P. Some of the new cars do have drain plugs in the gas tank. good luck!

whimps...a simple hole in the tank with a brass punch works best....catch fuel with a funnel into gas can...presto-done