Several factors work together to influence your admission and they broadly fall into two categories:
Those that you can no longer influence
Your academics and work experience are the two most important parts of your past that determine your chances of admission.
Some of you may have good grades to boast of, may have studied in good colleges or may have received awards and distinctions. But, if you don't have much to boast in terms of your academics, focus on you work experience.
The number of years of work experience makes a difference. The longer you may have worked, more the opportunities you are likely to have had to prove yourself. The quality of work matters more. You need to focus on your achievements and the extent of your exposure to different business functions. Think about the responsibilities you handled, your initiatives and the learning you took from them.
Those that are still in your control
A high GMAT score is important, 700+ is a good target to work on, if you are aiming for the top schools.
The right choice of recommenders can make a difference. Choose people who know you well, have seen you at work, and can give a true opinion about you.
Application essays are meant to describe your past achievements. You must work hard at identifying and projecting the right accomplishments. You need to make sure that all the essays together convey your all round abilities. Project your big achievements and those finer parts of your personality that may be the basis behind your achievements.
MBA Essays - 8 steps to make them effective