(MONEY Magazine) – As college students get set to crack the books for the 1991-92 school year, their parents might like to know the best-kept secret about financial aid: it's often negotiable. That's one of the important facts reported in the upcoming MONEY Guide: Best College Buys (available on newsstands for $3.95 beginning Sept. 9; copies of the magazine can be purchased by mail for $4.50 by writing to P.O. Box 30626, Tampa, Fla. 33630). For proof of the kind of give-and-take that goes on between students and financial aid officers, just ask Stanford University junior Michelle Mello , (right). Through persistent letters, phone calls and visits to her college financial aid officers, Mello badgered Stanford into giving her the extra $500 loan that she needed to stay in school. If you get a lowball aid offer from a school that your child wants to attend, try a reasoned and documented appeal to financial aid officers. Draw attention to any special aptitudes or talents that your child has, such as musical or athletic ability, and request more help. You may be able to convince the financial aid office that your child is something special and deserves more assistance, says Donald Moore, director of financial aid at the State University of New York at Oneonta. You may even be able to play one school's aid offer against another's, if the colleges consider themselves to be academic equals. ''If someone shows us a scholarship from another competitive school, we'll take a hard look at it and may match it if we consider the student very desirable,'' says Walter Cathie, associate vice president for financial resources at Carnegie Mellon University in Pittsburgh. At most schools, sought-after students can get more attractive deals than the standard awards through what financial aid officers call preferential packaging. The term, which you won't find in any college's promotional materials, refers to the practice of offering aid packages sweetened with lots of grants and scholarships to students rated most desirable by the admissions office. Recipients can be brains, jocks, minorities or even geos -- financial aid jargon for kids who hail from states that aren't well represented on campus. To qualify as an academic all-star, your child will have to rank in the top 25% of students that the college has admitted, based on high school class rank, grade point average and college entrance exam scores.

CHART: NOT AVAILABLE CREDIT: Sources: Peterson's Guides of Princeton, N.J.; the schools; MONEY estimates CAPTION: WHERE GRANTS ARE GREATEST These colleges and universities provide the largest average grants to students demonstrating financial need