What is the correct protcol for Keurig coffee maker usage?

Are you supposed to leave your old K cup in the machine so the next person has to remove it and throw it out? Or, do you remove the used K-cup immediately and toss it when you take your full mug?

I was recently given a machine and am new to this trend. I am old-school and prefer to make a pot that costs a few cents per cup while bathing the house in the delicious aroma of French grind.

I find it difficult to accept paying about 50 cents per cup for something that is half plastic and foil and requires the expense of another 50 cents if I want a warm up. That warm up can only be in 6, 8, or 10 oz increments so I must be careful to not overflow.
If I’m going to pay $1.00 for a coffee I’ll eat at Joe’s where the waitress calls me “Hon”, asks me how my kids are doing, and keeps refilling the cup until I have get out my seat with my knees pinched together.