Apply for a scholarship. There are merit based graduate school scholarships out there so start doing some research to find them. Talk to the admissions office at the college or university at which you'd like to apply. They can give you advice on applying for their own scholarships (if they have them) or point you to the appropriate federal and/or state scholarship programs. Even doing a search in Google for 'graduate school scholarships' pulls up a huge amount of information.
Look into a fellowship or assistantship. Many colleges and universities offer programs that enable you to get a master's degree while doing research or assisting professors in the department in which you wish to study. This is a viable option that also enhances your hands-on experience in your chosen field.
Talk to your employer. Many employers are willing to foot the bill for a master's degree, especially an MBA (Master of Business Administration). Talk to someone in your company's Human Resources department to get more information.