I just finished up a coolant leak a couple of weekends ago. As it turned out, I had to replace the thermostat cover, the thermostat, upper & lower radiator hoses, and last but not least, the radiator itself.
I'd suggest starting off by spraying down your radiator and hoses with a garden hose, this will clean everything off, and help you spot the source of the leak. After the coolant dries it will leave this white looking residue.
You might want to take off the front splash pannel thing, this will let more light in, and also you can check out the bottom of the radiator but getting up under there.
I guess another thing to think about is where in relation to the engine the puddle is. If its up front, it could be a different problem from near the back of the engine.
Good luck!