how I prepared for GMAT

1. Take a free mock test (not the GMAC one) to baseline your strengths and weaknesses.
2. Purchase the GMAT Official Guide (latest edition). Solve this back to back.
3. Take the GMAC free mock test. GMAC mocks closely resemble the actual GMAT. GMAC is also the body that conducts the GMAT.
4. Purchase a pack of GMAC free mock tests. Do them.
5. Very important - spend time analyzing where and why you made mistakes. Did you forget the formula? Did you not know the formula? Silly mistake? This helps avoid the same mistake twice.