The seven Leave no Trace principles are listed below:
Before you leave on any trip, you should have a detailed plan with your group. Planning ahead can help make your trip safer, and can help reduce any damage inflicted by your trip. You should consider planning your exact route, where you will be staying, how you will dispose of waste, when will you be going and how the weather will affect your trip, any applicable regulations, and the skill of your group members. There are many things to take into account when you are planning a trip, try to account for as much as you can, it will make the trip more enjoyable for everyone involved, will make the trip safer, and will reduce your impact on the environment. Planning ahead could include bringing maps of the area you will be visiting, so you will know where trails are located.
If you've ever gone to camp, you've probably heard someone tell you to only stay on marked trails. That direction is based on this point of Leave no Trace which asks you to minimize any damage you create when traveling and camping. If you are traveling in a location where an established trail exists, you should only use that trail whenever possible. However, if you must travel where a trail doesn't exist, you should, to the best of your ability, travel on surfaces that will not be damaged by your travel, such as water, rock, sand, or snow. Walking in places where there is no trail could disturb existing plant and wildlife.
This point can be summed up simply with the statement "Pack it in, pack it out." Anything you bring with you on an event needs to leave the wilderness with you. The most pressing concern for leaving waste in the environment is human waste; if designated bathroom facilities are available, use those. If you are traveling to an area where bathrooms will not be present, refer to the official Leave no Trace website or ask your trip leader. Food waste may not be dispersed into the environment. Any food waste generated must be consumed or packed out with you. Food will attract wild animals and can have negative effects for both the animals and future travelers.
The outdoors exist for all of us to enjoy. To help ensure it stays pristine for the next visitors, leave everything as you found it. Do not modify your campsite in any manner that will affect the next visitor, do not harm any plants or animals nearby, and don't take artifacts you find with you. Think about it this way: if everyone visiting a site took something back with them, eventually there would be nothing left to go see.
While campfires are a tradition of camping, they may not always Leave no Trace. A good fire will leave no evidence that it ever occurred. Check with the land manager or ranger of the area you are visiting to see if campfires are allowed before starting any fire. Care should be taken to ensure that there is no environmental damage as a result of your fire. You should use a designated fire ring, or if one is not available, mineral soil can also be used. A fire should only last for as long as is necessary, and should be no larger than needed.
When traveling and camping outdoors, you are a visitor in the animals' homes and care should be taken to ensure a minimal impact on the animals. You should never attempt to attract the attention of animals or disturb them as this can be stressful to animals. Water is a precious resource to animals and you should ensure that you are never blocking an animal's path to nearby water and make sure that you aren't contaminating their water.
Camping in the outdoors is amazing, but part of the greatness comes from the feeling of solitude or relative aloneness. Take care when you are camping to minimize your impact on other visitors. You should attempt to remain quiet so as to not disturb other visitors.
More information can be found on the official site for Leave no Trace.