I really wish I could summarize this is on 1 post. However I cannot.
For starters do this:
1. Download the GMATPrep from mba.com and take it to see where you stand.
2. Pick up the Official Guide 12th edition as well as the Quant and Verbal supplements.
3. Pick 1 test prep company and either sign up for their course, or buy the book(s).
4. See if your scores improve by taking another test.
5. If yes then take the real test.
6. If not delve on the specific areas of difficulty. Use the support system at your test prep company or these forums to address them.
7. Repeat above process till your scores increase to desired level.
8. Take the real test.
And yes - make sure to stock your fridge with some cold beer. This is going to be a bumpy ride - but hang in there!
HTH,
Arun