GMAT Club Tests - Must Have for Success

Introduction:
GMAT Club Tests are by far the the most powerful resource available in the market today.
The GMAT Club community has created such a valuable resource - it's a shame if one can't leverage it to get the best possible score.
Each question goes through an intensive peer-review process. The moderators are very responsive - quality issues get fixed very fast. This ensures a level of quality that most other test-prep companies are unable to match.
Trust me on this. I had once sent an email, pointing out a typo to a big-name test-prep company. A couple of days later, I received a boiler-plate response directing me to their (paid) one-on-one tutoring service. :)

Huge shout out to bb, Bunuel, chetan2u, GMATNijna, sayantanc2k & souvik101990.
You guys are awesome! :)

Sectional Test vs Full Mock?
When I was just starting my preparation, I used to think that since these tests aren't as good as full mocks. Unlike full mocks, GMAT Club tests are sectional since verbal & quant tests need to be written separately.
Well, I was wrong! I realize now that sectional tests are much better for practice. You can customize your practice towards the areas that you need to focus on.
In my case, my quant ability was weak. I started from a Q39. With regular practice was able to push it up to Q49 (latest official mock).

How I used GMAT Club Tests?
As a working professional, I used to study for 2 hrs every day.
I used to take a quant test early in the morning.
Then, over the next two days, I used to review my responses.
On the fourth day, I used to write another test. Rinse, repeat.

My Approach to reviews:
On average, I spent twice as much time on reviewing tests as I did writing them.
Here's how I review tests:
1) Solve all questions.
2) Check whether I can solve the question within 2 minutes.
a) If I can't, check for alternative ways of approaching the problem on the forum.
b) Finally, add the question to my error log (Anki).

Pros
1) Questions are of high-quality.
2) The product is very affordable (Value for Money).
3) Less time needed - ~1 hr vs 3 hrs for full mock.
4) Quant Tests are a bit more difficult than the the real GMAT - that's a good problem to have.

Cons
1) At the advanced level (~V40), you may need to supplement the Verbal Tests with other material such as LSAT.

TL;DR:
Overall: Best practice tests available in the market today.
For Quant: You can't go wrong with these tests.
For Verbal: For advanced level (~V40), may need to supplement with LSAT materials.