I was in the same boat as you are. I was scoring 50/51 in quant, but my verbal score was between 17 and 20. Now, I am writing my practice exams, and my scores in verbal are between 38 and 45. I am going to share how I am improving (since I am still working to improve my verbal, I say "am improving") my verbal.
I am following the following materials:
1. LSAT tests and explanations from Kaplan.
2. GMAT 31 sets.
3. OG 10+11+12.
4. GMAT old paper tests.
5. 1000 SC.
How I am completing these materials:
Step1:
1. Take the LSAT tests in a test mode. You will have two problems at the initial level: Time problem and lots of mistakes. Ignore time at the very beginning because you must first know which ball should be beaten in which way. If you don't know how to walk, you should not run. So, ignore time and number of mistakes.
2. Read explanations from Kaplan. Those explanations are informal. It will make you understand everything in an informal way. You will feel very homely while you are reading the explanation of Kaplan.
3. Make an error log of the mistakes with types of question. Say for example, you make mistakes in the tone questions of RC, you will mark it as your priority, and you will read the explanation on these things very carefully. Try to find how answer tone question. How did the writers of the explanations go through the questions?
4. After taking the first 10 tests, you will see an improvement, because till now you have already completed 40 RC's and 540 CR's. At this point you will begin to be careful about time. Take the test on time condition.
5. There are 40 LSAT tests, which are available on the web site. DO THEM ALL.
6. MIND IT "PRACTICE, PRACTICE, and PRACTICE" can help you to improve verbal. There is no medicine.
Step2:
1. Write explanation of at least 10 GMAT sets. Writing explanation will help you how attack the question.
2. Take 21 GMAT sets on time condition.
3. Maintain an error log for every question you get wrong.
4. Write explanation for those wrong questions.
5. Review your error log at least twice in a week.
Step3:
1. Read all the verbal questions of OG10. There are lots of SC, CR and RC in OG10. Read carefully all the explanations.
2. Read OG11 and OG12 carefully. Read all the explanations until you get ideas in habit. Since these explanations are written by the test writers, their attacking styles are important. Try to catch the styles.
3. There 10/11 paper tests. Attempt them on timed condition. Explain them.
4. READ ALL THE OG's at least three times.
Step4:
1. Take practice test of all 1000 SC. You can take 50 SC at a time. Then review them.
2. Make an error log for wrong SC's. Search explanation through google. If no explanation is found for any question, you will post them in any one of the forums. Specially BTG, URCH, GMATCLUB. You will see lots of people around you who are always willing to help.
Steop5:
1. Read the "science daily". At least two articles should be read. You will read them to know what is happening around the world. Actually you will increase your endurance to read odd thing that you don't like to read in a normal situation.
Motivation:
I know some people on different forums who have developed their verbal scores from scanty 15 to 35+. I have seen one person who was scoring between 20 and 22 in verbal. After four months he improved the verbal score to 36. What he says is practice.