Review the checklist of items needed to complete the MBA application for the school you are applying to. Common items are letters of recommendation, essays, GMAT scores and a completed questionnaire containing your personal information.
Start completing these items well before the due date. You do not want to have to ask someone to write a letter of recommendation for you at the last minute, or to write your essays quickly without putting much thought into them.
Proofread your essays. After you have done this, have someone else whom you trust look them over. If possible, find someone with a writing background to read them and provide you with suggestions for improvement.
Gather all of your application materials together. Review your checklist one last time. Make sure you have everything you need, then put it all in an envelope and mail it off to the school.