First, overall, don't pick a test date yet. Nobody can predict exactly how long it will take them to study. You can have a general time range in mind, but you may need to alter that timeframe depending on how things go.
Next, are you studying on your own? Taking a class? What have you done so far? What materials are you using? What are your strengths and weaknesses? There isn't a one-size-fits-all plan - we have to figure out what will work for you, specifically.
Read this:
http://www.manhattangmat.com/blog/index ... an-part-1/Make sure to read both halves (the link to the second half can be found at the end of the first half). That article also contains links to a number of other articles. Follow them.
After you've done that, and after you've followed the instructions in the part about analyzing your practice test, come back here and tell us what you learned about your strengths and weaknesses. Also tell us what kind of plan you think you need to follow. We'll then tell you what we think about your analysis and your plans! :)