What are best GRE prep for improving Verbal and ace Quant ？

[carrieinus]

I got V:137, Q:158 without any prep for the first time I took GRE just yesterday.
I have prepared for GMAT for months and did not have a tremendous improvement, and some deadlines of master degree within in 20 days. 
I sentence completion is my weakest spot.

[historicallinguist]

Usually, you cannot improve too much in 20 days, and you probably need more time.

[khigh]

You won't make it by your deadline.  You can only test once every 21 days and it takes 10-15 days to get your report back.