In his book 'Happiness - the science behind your smile', Daniel Nettle introduces three definitions for happiness: as a momentary feeling of joy or pleasure (level 1); as a judgement about feelings, like contentment or satisfaction (level 2); and as a reflection on a life trajectory, like flourishing or fullfiling of one's true potential (level 3).

Based on his ideas, here's three ways of living your life to achieve happiness:

1 - Carpe Diem: Eat, drink, and be merry!
(Hedonism, or the joyfull life - 1st level happiness)

You like parting all night? All right! You like playing games all day long? Go for it! Life is too short to not get what you want right now.
Just remember the hedonic treadmill - once you party everyday, you either need better and better parties or you will get used to the same thing every day.

One realistic aproach to this way of life was invented more than 2000 years ago in ancient Greece by the Epicureans: seek a simple life with modest and sustainable pleasures and a state of tranquility and freedom from fear and pain. Simple things like eating, drinking, resting, all in moderation. Once you are content with a simple meal, a simple house and a simple life, it will be easy to be happy every day.

Examples: Thomas Paine, Thomas Jefferson, Ayn Rand and Christopher Hitchens were famous self proclaimed epicureans.

2 - Follow the yellow brick road
(Satisfied Life - 2nd level happiness)

Every society has a program on how one should live his life, designed and refined in generations of struggle, based on your culture, who you and your family are and what your society expects from you. Learn this path and follow it to the letter, be the best of it and reach the summit of your possibilities. Then sit back, relax and enjoy the ride.

Much of what we desire or want to achieve is deeply connected to our upbringing and culture, in a way priming us for success in a local context. Of course there will be people more popular, wealthier, prettier, or better than you in any way, but if most of our needs are covered and we are surrounded by friends and family sharing and aproving our way of life, you should be able to live a happy and content life.

Examples: In Brazil, once you're born, you go to the best school possible, and study as long as you can afford (finish the high school at least, but get an University degree if possible) - ah, and while you do that, please find the love of your life. Then, you find a well paid stable government job (at the natinal bank or post office, or any government ministry position), get some loans, buy a car and a house. Finally, you extend your family, having as many kids as you can afford (usually 2), and put them in the best school possible, so the cicle can continue.

3 - Take the road less traveled
(Fulfilled life - 3rd level happiness)

You saw your options and decided that's not for you: you know better, and deserve more from life (or don't know yet and want to find out by yourself). Ok then, but remember - the road less traveled is much harder to walk, you will find many obstacles in your way, most people will not understand your decision and will in fact actively discourage you all the way. And once you get there, there's no garantee of happiness (at least using the previous definitions of happiness), except for the inner pleasure of saying: "I did it my way!". Maybe after you're gone, people will recognize your efforts and applaud you as a genius ahead of your time, but then again, maybe not.

To do that, first know thyself! What motivates you, what is your passion, what would you do no matter what? Try to get really good at it, maybe with studies (get an university degree), maybe with practice and experience (join an apprentiship, get a mentor), and once you feel confident - set sail! Remember to follow your instincts - where you are going there are no paths to follow, and possibly all external advice may hurt more than it helps. But try to use the golden and silver rules as a inner compass: treat others as you would like others to treat you, and don't treat others in ways that you would not like to be treated. 

Example: Many exceptional people decided to forego traditional 'happiness' in search of a higher calling, like Mother Theresa and Gandhi, but not all were celebrated during their lifetime, as philosophers Friedrich Nietzsche (who suffered a mental collapse  in 1889 and was diagnosed with "manic-depressive illness") and Ludwig Wittgenstein (a notoriously tortured, melancholic and irritable man who requested on his deathbed - "tell them I've had a wonderful life!").

Do you agree, disagree, or have more examples to add? Share your thoughts in the comments!
And lastly, be careful with anyone's advice, including (specially) from people that don't know you (like me).