Leave only footprints. Take only memories. Kill only time. Taking care of the backcountry is a responsibility, not an option. For more details on low-impact hiking, visit the Leave No Trace web site.
Fires scar the land.
Run-off from soap, or worse yet, contamination from human wastes can cause a wide range of problems. Keep the noise level down - it keeps the hike enjoyable for others and increases your chance of viewing wildlife. Pitch your tent in designated camping areas only and use tent pads when they are provided.