When you venture beyond the campground into the backcountry, you'll find there are no nice, smooth camping sites just waiting for your tent. You take on the responsibility of finding your own home for the night and choosing the right tent site. While you may come across previously used sites if you're hiking a popular trail, often there are none, and you must know what to look for in a good camping site.
Choosing your tent site actually starts in the morning when you are preparing to start hiking. Decide how far you want to hike that day, take a look at your map, and find a water source to shoot for at that distance. Then that afternoon, as you approach the target water source, begin watching for good spots for the tent. Try to use an existing campsite. This minimizes the impact to the environment and helps keep the wilderness in a condition for everyone to enjoy. If there are no existing sites, here are some things to consider as you choose your site.
You'll want to be near water so you don't have to carry it so far, but set up camp at least 200 feet from the water source to safeguard against contaminants being washed into the water supply.
Try to put your tent on the highest spot so any rain drains away. Low spots collect water, and damp areas are often swarming with mosquitoes and black flies. Consider the season -- will you want shade to keep cool in the late afternoon, or will you want the sun to hit the tent early to warm it up? Situate your tent accordingly. Steer clear of poison ivy patches and stinging nettles or other poisonous plants.
Look down. Pick an area free from rocks, roots, or lumpy ground. It's okay to remove loose branches and debris, but don't chop live branches or dig rocks out of the ground. Then look up. You don't want to camp below a dead branch that might fall on your tent during the night. Now look around. Are there good tree branches to hang your food bag from? Hanging your food helps keep it safe from animals.
Know the regulations concerning campfires where you are hiking. If fires are allowed and you plan on having one, try to camp in an area with plenty of dead, downed wood. Never chop down a living tree for a fire; it won't burn anyway.
As you pack up in the morning and prepare to head down the trail, be considerate of the wilderness and of the next hikers to come through. Douse and stir the coals from your fire until you are absolutely sure they are cold. Make sure you pick up and pack out your trash, and try to make it look as if no one has camped there.
You won't always be able to find a campsite to satisfy all the criteria, but with practice, you'll know where you can compromise and still have a safe, comfortable camping trip.