Improve your grammar: I worked very hard over the last year for GMAT®...

[Brice]

I worked very hard over the last year for GMAT. Unfortunately I was barely able to cross the 600+ mark. The results were dismal compared to the labour that I had put in. This has shattered my confidence. However, I have picked myself up and plan to give it another try this year. I need some sure-success mantra.

[Rosee]

can any one tell me some tips to enrich vocabulary. :?

[Snatty]

[Chocolatte]

I think that the attitude you have approaching this second attempt is already a great step to succeeding! Sometimes we are taken slightly off gaurd when it comes to test taking, particularly when it is a very defining exam. Now, though, you have some experience with the format, timing, and sections of the test. This should be helpful when you are going through the exam for a second time. Continue with the rigorous preparation just as you did the first time you were taking the exam and I think you should definitely see an improvement in your scores! Best of luck on your second round!

[Shivgan3]

One way to learn tough words is to create links to the word from various approach, from thesaurus / images / mnemonics etc.
There has been various sites that can help you to practice the new words you learned.