How does one become a Grand Master

how does one become a Grandmaster.

The same way one gets to Carnegie Hall - practice, practice and practice.

In the meantime read this

http://en.wikipedia.org/wiki/Grandmaster_%28chess%29

Win a bugger of a lot of chess against increasingly strong opposition and study really hard with some exceptionally good teachers until you win enough tournament placings against GM opposition that you get awarded the title yourself. But if you're not there by age fifty, your chances are poor (and don't I know it).

The above is voided if you happen to be Capablanca, learn the game by watching your father play, beat the first unsuspecting club player who gives you a Queen start because you're under five, win the championship of Cuba at your first try, and later impress the reigning world champion enough that he is moved to offer you the world title without a contest, and when he actually plays, score four wins against none before he resigns the match. But you only get to be him once a century.

Is it necessary to have a rating of 2500  or are there other requirements.

http://en.wikipedia.org/wiki/Grandmaster_%28chess%29

 I think become a grandfather would be easier.

First, build a box of wood and construct candles in an alternating pattern all around it. Burn incense and take a twenty dollar bill, which you will burn upon the wooden altar while chanting the magic mantra of, "Oma, Loma, Raku." At this point, Caissa will appear. Appease her by stripping off your shirt and showing her your bulging biceps and washboard abs (If the latter doesn't exist, you must fulfill these prerequisites before proceeding with the construction of the altar). At this point, she will kiss you upon the head and vanish. Suddenly you will feel dizzy. You will fall to your knees as you gaze up at the sky, feeling variations pump into your brain. You have now memorized all subvariations of the Sicilian Najdorf Main Line, as well as numerous theoretical positions and first-class opening theory, such as those from the Ruy Lopez and the Catalan openings. Your tactical prowess will put Garry Kasparov to shame as your rating strength flies to 3000 - the first human to pass the 2000 barrier. At this point, you must open your eyes and -

REALIZE THERE ARE NO SHORTCUTS! HARD WORK WILL GET YOU THERE!

(Although one of my friends is a GM, and this is what he did ... perhaps, there is hope ... )

Chew a lot of gum? It seems to be working for me. I started chewing bubble gum a couple months ago, and my rating has risen from a mere 800 to almost as high as yours!!!!!!

Look into the FIDE Handbook

 It could be, but I think all that wood-shoving has more to do with it. :D