Warm-up before starting the hike.  We cannot emphasize just how important stretching out before a hike truly is.  Stretching increases the heart rate, temperature, and blood circulation to your muscles.  Moreover, stretching increases the body's flexibility and decreases chance of injury.

Start the hike off slowly.  Once again, it is important to warm your muscles and body up before trekking forward full steam ahead.  Gradually increase pace as your body begins to heat up.

Allow the slowest person in the group to establish the pace.  The best way to accomplish this is to let the slowest person lead the group.  Injuries and exhaustion can frequently be avoided by letting young children and folks who are out of shape head out first down the trail.

Plan the hike ahead of time.  This can include assigning tasks to various members who will participate on the trip.

Figure out who enjoys leading and who doesn't.  Once you figure out who enjoys making decisions and leading various aspects of the hike, make efforts to divide decision-making responsibilities evenly amongst those people.  However, it is important to stick to the trip itinerary unless an emergency dictates otherwise.

Stick to the trail.  Don't stray from the trail unless you possess excellent navigation skills and the area will not be negatively impacted by off-trail travel.

Travel in a group.  This principle holds especially true during the winter and in hazardous terrain. 

Give your trip itinerary to a third party.  Leave your trip information with someone who you can trust (friend or family), and contact them when you get back home from the hike.

Learn first-aid and basic gear repair methods.  Always bring duct tape with you wherever you go.  Duct tape can mend just about any piece of gear that you might happen to break while out on the trial.  Don't forget to bring a first aid kit!  Finally, know what to do in case you and your group runs into an emergency situation.  It is best to discuss your "emergency plan" before beginning a hike.

Layer up.  Avoid wearing cotton because it loses its insulation properties when it get wet.  It is best to wear polypropylene next to the skin because the material wicks moisture away from the skin and retains heat when wet.

Protect your body from the sun. Wear sunglasses, a hat, and sunscreen anytime you go hiking.

Take adequate rests.  Don't overdue it!

Hydrate.  Drink sufficient amounts of water.  Make sure that you carry enough water to make it between destinations without running out of a safe supply.  Also, be sure to treat your water in order to avoid getting sick on the trail.

Pack plenty of food.  Energy and candy bars are some of the best foods to bring on the trail because they are packed with carbohydrates, which will give you the boost you'll need on the trail.

Adhere to relative rules and regulations.  Take some time to read over the rules and regs of the area that you'll be traveling through.  Some areas might be off-limits to pets and open-pit fires.