I occasionally, especially after a trip through the mud, remove the electric fan and shine a flashlight from the motor side out (works better at night), they can be clean on the front and dirty inside. At most anyplace, that sells refrigeration supplies, you can get a fin comb, helps cleaning the condensor without bending the fins (much).
I´ve had leaks, that were in spots, where the coolant evaporated almost as soon as it leaked out. Often a white stain or a stain the color of the coolant, where this is happening. Like mentioned before, the bottom radiator hose (engine side) is a prime spot to look. Under the pressure bottle, is another. Rubbing likely areas, with a paper towel, will often show some color (red/green withever color your coolant is). A very small pinhole leak in the radiator is also a possiblity. Look for places the radiator fins look roted (or green), often down low (on the inside), seams sometimes split and throw a coolant mist out.
If a head gasket is bad and coolant is getting in the oil, the oil level will rise on the dipstick, oil often looks like a mocca milkshake.
If it´s getting into a cylinder, overheating is often the result and the coolant foams in the surge tank. Rubbing a paper towel lightly at the exhaust opening after start up (not the soot, just the liquid)will often show a stain the color of your coolant (if the head gasket is leaking). There are better tests, these are just indicators.