Whether you camp in a park or commercial campsite, or somewhere out in the wilderness, the most important part of your camping trip is at the end when it comes time to clean up the campsite. If you're in a national park or commercial site, this may mean cleaning up after campers who are less considerate of the environment. If you're camping in the wilderness, this will mean making your campsite look like no one has ever been there.
No matter where you're camping, the primary concern during cleanup will be making sure your campfire is completely extinguished. Follow the simple steps of Douse, Stir and Feel:
Douse the coals - slowly and carefully so as not to cause splattering or clouds of steam with ash in them.
Stir the coals - making sure that all are wet and that there are no hot coals or embers.
Feel the coals and/or fire ring - to make sure there is no heat.
Repeat until all coals are completely soaked and there is no heat emanating from them and from the fire ring.
DO NOT bury hot coals, they are still a fire hazard that can smolder and spread.
If your campsite is in a national park or commercial site, you will most likely have trash cans available in order to dispose of all garbage properly. If you're in the wilderness you will want to observe the "if you pack it in, then pack it out" rule. In other words, if you brought it in then you take it out. Food or product wrappers, twist ties, bread ties, paper, plastic, cigarette butts, cans, bottles, and all other garbage, including food remains, need to be removed, packed up securely and taken back out with you. That fire that you put out completely earlier? Make sure you remove any newspaper or firestarter material that may remain, as well as aluminum foil, plastic, metal or any other non-natural material. Again, the bottom line is if you brought it in, you take it out so that you leave no trace of your presence.
If you were camping in the wilderness and had to make use of a "wilderness bathroom", be sure that you have filled in all holes completely and restored any surface coverings (rocks, moss, branches, etc.) you may have moved. Likewise if you made use of area rocks to form a fire ring, be sure to return them all to their original locations AFTER they are completely cooled.
It is the responsibility of all of us to be good stewards of the land we enjoy and the environment.