Rule Number one... Respect.

Respect is sometimes considered a formal word.  It's something that applies to your boss, teachers, mentors, even colleagues.  It's not usually something you think of in your everyday interactions.
But it should be.
It's not something reserved for the highest and noblest in our lives.  It's not something that only comes out when we're at work, or at an important function.  It's not a song.
It should be a fundamental part of everything you do, of who you are.
Let's look at the word respect.  According to Old Man Webster, respect is "a feeling or understanding that someone or something is important, serious, etc., and should be treated in an appropriate way."
Wow.  Noah Webster nailed it.  Someone, or something, is important.
That, right there, is the key.
Everyone on this planet, from the highest and most famous celebrity or politician, right down to the humblest beggar, is worthy of basic respect.  Everyone has worth, everyone has value.  Some, unfortunately, choose to disrespect others, either through words or actions.  But that person has the capability, at any time, to turn around and make amends.  It is still possible, no matter how unlikely, that they can improve themselves and show respect to others.  They should still be respected as a fellow human being with human rights.
So, how does this apply to life in general?  Why should respect be rule number one in life?  Well, people tend to learn best through parable, simile, metaphor, fables, anecdotes... by the example of others.  So let's try one, shall we?

You are at the store.  It has been a very long day, you have kids in the car begging for the latest sucrose-infused hyperactivity inducing indulgence in the bags, you are exhausted, you haven't showered for three days, you blew a tire this morning at the very beginning of your errands, the wind is blowing and fighting your efforts to load things into the car...
And then it happens.  Your cart skitters out of your control, and bangs into the car next to you.
Oh....no.
You yank it quickly away and examine the car.  There doesn't appear to be any damage.  Cars are much hardier things these days, partially made of plastic and rubber, and less prone to minor bumps and scrapes.  Phew.  Now all you want to do is get the heck out of there as fast as humanly possible, plunk the kids in front of a movie with their treats, and have just five minutes to sit down before your body chooses to force you to do so anyway.

Let's switch perspective to the owner of the other car.

It's been a long day.  Your car wouldn't start this morning because of a dead battery, you were late to work, and immediately got yanked into a meeting during which you learn that the firm's biggest client just decided to jump ship and go with your strongest competitor.  The boss, whether unfairly or not, decides that this is all your fault and proceeds to rail on you for the next half hour in front of your colleagues, all of whom are giving you covert smug looks that say "well, nice knowing you, pal, can I have your office?"
You wife calls during lunch to inform you that three of your offspring have the flu and have been throwing up all morning, which causes you to instantly lose your appetite.  As much as she would love to send you to a hotel to avoid the plague, she desperately needs your help.  Oh, and could you stop at the store and pick up something easy she can shove in the nuke-box because she is busy cleaning up a dozen piles of vomit on the white rug, and oh yeah, you need another bottle of carpet cleaner.  Or two or three.
The cashier is extremely slow, and surly, glaring at you as if blaming you for every minute of their miserable minimum wage existence.  You grab your purchases and swiftly head for the exit, vowing to wreak vengeance on the next person who so much as breathes at you wrong.
You get outside and down the row of cars just in time to see some jerk hit your car with their grocery cart.  Unbelievable.  You stride over, blood boiling, preparing your best "what idiot school dared to spawn such a stupid, inconsiderate punk as you... and by the way, you're going to pay for that."

Switch back to the mother with the cart.

You turn around, and see a guy coming toward you with thunder in his face, fists clenched, keys in hand.  The owner of the car.  From the look on his face, he is utterly furious, and about to explode on you.  Fear rises in your throat, choking you.  At the same time, your hackles are instantly raised, like a stray cat facing a pack of rabid dogs.  He looks ready to give you one heck of a battle, and you are ready to return fire.

Now stop.  Step back from either perspective, and look at the situation.
Both of these people have had a very bad day full of disrespect from their fellow human beings.  Frankly, they haven't really deserved any of it, and they feel it.  They feel beaten, exhausted, and ready to snap.  Neither one did anything deliberately to hurt the other, and yet they are both angry at either other.
Throw in just a dash of respect.  Tone down the anger, try to look at things objectively.  Is it really worth it?  Is it really worth the battle, the anger, the hurt that you might cause?

Hit the play button.  The car owner stops, taking another look at the cart holder.  She looks tired, nearly in tears, and already pulled the cart quickly away from the car.  She is clearly very aware of what happened, and feels terrible about it.  Is yelling at her going to improve the situation?  Is it going to make your miserable day any better?  Probably not.  You know yourself well enough to know that seething over the incident for the next three hours is not going to help anything.  You walk over without saying a word, focusing on your breathing to calm down, and examine your car.  No damage.  Thank goodness.

Switch to the owner of the cart.  He didn't yell.  You let out the breath you've been holding, unclench your hands, and explain in a shaky voice that the wind blew your cart out of your control, and it hit the car, and you are so very, very sorry...

Back to the car owner.  You can hear it now.  The pain and stress in her voice.  This is a fellow human being who has likely had just as bad a day as you, her kids are now whining and fighting in her car, upset at the delay in their routine, and she really doesn't deserve to be yelled at yet again.
"It's okay," you finally manage.  "There's no damage.  You might want to brace your cart on your bumper next time, that usually works for me.  Hope you have a better day."
She blinks, totally not expecting that response, then manages a weak smile.  You push the anger away, letting it drain into the cracked asphalt, and for an extra measure of forgiveness, you take her empty cart and put it into a cart return rack for her.  She calls a tearful thank you, climbs into her minivan, and drives away.
You put your bags in your car, climb in, and start for home.

Let's look at how both parties are feeling right now.  The owner of the car, instead of being angry at the situation for the next few hours, which isn't healthy, has decided to let it go, and show some kindness and respect.  He still has a long evening to face, but at least he can face it without yet another incident digging into his skin like a poisonous thorn.  He feels good that he chose respect, and made another person's day just a little better.

Look at the cart holder.  She is still exhausted, the kids are still whining, and there's that nagging ticking sound under the hood again... but she avoided a fight.  The car owner showed her kindness, and a feeling of gratitude and relief lightens her burden just a little.  Thankfully, there are still good people in the world.

Basic respect.  It really isn't as hard as it seems.  When you feel like disrespecting someone, through anger, fear, embarrassment, or sheer exasperation, stop for a second.  Step back.  Is it going to help the situation?  Probably not.  Do they really deserve it?  Not likely.  Is it going to ruin your day?  Oh yeah.
Turn it around, and look at it from the other person's point of view.  Most of the time, they don't mean to hurt you.  There are very few people that go around all day deliberately being jerks.  When someone deliberately tries to hurt you, the best response is none at all.  Ignore them.  They thrive on your angry response, on knowing they have power to hurt you.  Take back the power in the situation, and don't let them manipulate you.  Respect that they are humans, and possibly have some kind of mental issue going on that makes them this way.
For everyone else, take a look at the possible outcomes.  Being angry and disrespectful isn't going to help either one of you.  "But I want to teach them a lesson!" you say to yourself.  Honestly, they probably already know.  In the heat of the moment, in the midst of their daily frustration and the plague of details that hovers around them, maybe they just forgot.  It could even be something that is totally out of their control.  There is saying that we are our own worst critics, and it is very true.  You don't really need to yell at someone that is already beating themselves up.
And is it going to help you to yell?  No.  Medical studies have proven that the effects of anger can be very dangerous.  Even fatal.  Prolonged anger can cause problems all over your cardiovascular system.  It makes you tired, it makes you sick, it doesn't really help anything.  Even that small, momentary feeling of satisfaction at having scored a point wears off quickly.
Try respect, instead.  Take a step back, and if you can't speak kindly, or at least tolerantly, then don't say anything.  Don't make the situation worse than it already is.  You never know what someone has gone through, you don't know what makes them the way they are.

Or maybe you do.  Maybe this person is a member of your family, or your circle of friends.  Maybe they have done something utterly boneheaded, and needs correction.
Do you really have to be disrespectful about it?
No.  Of all people in our lives, our family and friends, those we love, deserve our respect.  Why is it that we are always more respectful of strangers than those we know?  "They should know better!" You say.
Yes, perhaps they should.  But they...are...human!  They are not perfect!  And neither are you.
Apply the same principle to your children, spouse, siblings, and friends.  Take a step back.  Look at the situation.  Knowing them as you do, you can probably figure out fairly quickly why they behaved badly.  Why they made a mistake.  With kids, you sometimes have to get tough.  But you don't have to be disrespectful about it.  Correct their actions.  Then show them that you still love them.  They aren't bad people.  They just made a bad choice.  You will get fair better results from love than from any kind of brute force.  Children learn from our examples, and if we choose disrespect, what do you think they are going to learn?
At our core, we genuinely want to be liked.  We want to be loved.  And we crave respect, we crave the connection that can come only from love and kindness.  There is far too little of it in today's world.
"So what good is it going to do?" you ask in despair.  "If everyone else out there is being a jerk, what good will it do to be nice?"
You may not know for sure.  You may never know what a smile, a kind word, an act of forgiveness may do for those you interact with.  Your reaction could be the straw that breaks the camel's back.  Or it could be the very last lifeline they have, the thing that convinces them that maybe, just maybe, life isn't so bad.  There are still good people in this world, people that make it a bit better place.
Wouldn't you rather be one of them?