I worried a lot about this, too, because I worked my way through UG and have worked for the past few years. But the loans come in and you have a few grand to use on personal costs during the semester-- just budget accordingly. It is tight, but you can do it. Spend carefully, clip coupons and stick to a social budget so you don't blow your grocery money at happy hour.
I have an ING account --> I put my loan money for living expenses in here. Once a month, I deduct a "paycheck" into my checking so I can pay bills, buy food, etc.
Start saving some money now and see if any family members can help you out. Also, look at outside scholarships if you are a minority, from a particular city, etc. Also, most Greek organizations have graduate level scholarships --> I got one from my sorority. If you were involved with any national honors organizations like Golden Key, you may be able to get a scholarship from them, too.