You don't need to memorize, you just need to indentify in which problem types you are going to need to test special cases.

In number properties questions involving exponents, test the following cases.

1. A number greater than 1.
2. A number less than -1.
3. A number between 0 and 1.
4. A number between -1 and 0

This will ensure that you don't miss out on statements that are actually sufficient or vice versa.

On questions in which it is clear that odds and evens are involved, always check all possible combinations of odds and evens.

When prime numbers are involved, always test 2, because it is the only even prime number and usually makes or breaks a question.

Never assume anything that is not explicitly mentioned. For example, a lot of the time people assume that if x is an integer, it is a positive integer, when this is not mentioned. Also when it is not mentioned it is an integer, it could be ANY real number, so remember not to only test integer values.

You have to develop the habit of calmly and unbiasedly testing cases, and refusing to fall for a trap answer by jumping a step or making an unwarranted assumption.

As you practice more DS problems, keep track of the ones you messed up on or didn't understand. Post them on our forum for DS questions and we will help you understand the best way to solve them. All these practices will help you develop the habits necessary to ace any DS question easily!
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Good luck!

Thanks alba!

As I was doing more DS problems I noticed that another huge error I am making is saying something is not sufficient based on whether it is right or wrong, instead of whether it suffices to answer the question. Such as when something is not divisible by 6, I am quick to go "WRONG!", from all those years of trying to find the right answer, rather than any answer, in math.

I'm going to try this repeated exposure to math- hours a day, everyday and hope it makes me better. This is how I became an excellent speller.