those are my favorite. i would do them all day if i can sell them.
#1 valve covers.
#2 lower intake manifold
#3 oil pan. hard to tell when they leak if everything else is leaking onto it
#4 front crank seal. look for oil on the pass. side on the hood, and for an oil soaked belt.
if it has higher mileage, sometimes the timing cover leaks coolant. also i bet that the water pump is leaking. they only seem to last a few months.
also the trans likes to leak at the solenoid pack, pan seal, and diff seal
i would start with the valve covers and intake. its easier to do them both at the same time. wash the engine after that, then watch for further leaks.