1) How do you know when your hair is drinking a conditioner? What does it feel like or what can u see?
Hmmm......Good question. I know that you can do a test to check this. This is more of a porosity test, though. Get a cup of water, and put a strand of productless hair into the cup. If it floats, then most likely the strand is healthy(has sufficient moisture), if it sinks, then this means that you hair is porous(some have naturally porous hair, others from damage/dryness) and is sucking in moisture from the water. Maybe this test can help in answering your question.
2) How do you know if your scalp is oily or dry?
Oily scalp is just that......Oily.
My fiance actually has an oily and a dry scalp.
When it's oily, I can touch his head and my hands are covered with oil. And when dry, it looks like small, dry patches(not flaky).
With my hair(which is dry), my scalp tends to flake. And looks, I guess parched........ The coloring tends to look paler and pink when my scalp is dry.