I'll add that since the engine usually sits at a downward angle in the rear I usually jack up the rear of my car while the petcock is open, you'll get a little more coolant out. That's more for if you're removing the heads, since the headgasket coolant hole is blocked at the front anyway, but it will drain a little more. And just as an aside, if I am pulling the heads I'll drain coolant by pulling the lower waterpump bolt. The passanger side goes into the waterjacket. I drill a small hole in my drivers side lower hole on my blocks also. Just remember to use a little sealant on those bolts. Then you don't have use the block drains. If I'm pulling the thermostat housing or expansion tank I'll soak up some coolant in the manifold with a rag first also, just to lessen the chance of dripping antifreeeze into the engine when removing the manifold. It's all a little overkill but I don't like any chance of getting antifreeze in the oil.
