When to take the test: You must first decide on an ideal date for your GMAT. In addition to personal convenience factors you must decide on a test date depending on the application deadlines of schools to which you wish to apply and the time you require to be fully prepared to score well on the GMAT test. It can take up to a month for official score reports to reach the business schools and most schools expect official reports to reach them before their application deadlines. Most applicants prefer to take the gmat test about two to three months before the school's application deadline so that the time between the test date and application deadlines is enough to complete the application forms, write essays and arrange original documents and recommendation letters for multiple schools. Based on this, decide on an ideal test date for you.
Registering for the gmat test: After deciding on a date at your end, you must immediately check for availability of testing space at a location of your choice. This can be checked online by going to the official site of Graduate Management Admission Council (GMAC). The seat availability can change quickly. If you are sure about the date and if it's available, you should register immediately. You would need to pay the required fee of US$250 by credit card.
If you are an international applicant and do not wish to pay by credit card, you can register at the Regional Registration Centers (RRC) of GMAC in your area for gmat.