GMAT Strategy

Hi,
I have been preparing for GMAT for over 8 months.
I have read and solved the following books: Kaplan2014, Kaplan2012 and OG13.

I took GMAT prep test on: 30March/2015

Scored: 610

Quantitative score: 45, 68%
Out of 37 questions in Maths I had 15 incorrect .
8 questions incorrect in PS and
6 questions incorrect in DS.

Verbal score: 28, 48%
Out of 41 questions in Verbal I had 16 incorrect .
8 questions incorrect in SC,
3 questions incorrect in CR and
4 questions incorrect in RC

I then solved half questions from OG10 of all the above topics and gave another Gmat prep test on: 17/April/2015
scored: 540

Quantitative score: 42, 57%
Out of 37 questions in Maths I had 12 incorrect .
8 questions incorrect in PS and
4 questions incorrect in DS

Verbal score: 23, 30%
Out of 41 questions in Maths I had 16 incorrect .
8 questions incorrect in SC
5 questions incorrect in CR and
3 questions incorrect in RC
In this test out of first ten questions in Verbal I had seven incorrect.

I will be giving Gmat by first week of June2015.
Can you please suggest some methods for improvements for all the above topics and a study plan which can help me score 720 above on GMAT.
Thank you