No matter who, every GMAT expert would say one thing without fail - GMAT is a standardized exam. So, look for the patterns while solving the question as that is the best way to prepare.
So, here it goes - First the Major Flaws in Reasoning and then all the Patterns that I have studied or realized.
Flaws
1. Generalization Flaw -
In crude words - That which is true for one may not be true for all and vice versa.
To Elaborate - If decreasing the price of 1 commodity increases the sale volume of that commodity, we cannot conclude that the pattern will follow for the 1 more commodity or all other commodities.
2. Causation and Correlation Flaws - If 2 events A & B occur one after the other, it does not mean that A causes B. Both of them may just be Correlated. We need to satisfy all the following 4 conditions to conclude that A causes B.
a. 3rd event C does not cause B.
b. 3rd event C does not cause A & B simultaneously.
d. B cannot happen without A happening.
3. Statistical Flaw - They are of 2 kinds
a. Large Numbers do not mean Large Percentage and Vice Versa.
b. Increasing/Decreasing Numbers do not mean Increasing/Decreasing Percentages and vice versa.
Patterns
Let's try to divide them as per the question types:
Stimulus
This pattern is the most common one in the Stimulus

Question starts with One point of view by one person or a group of people and then go on to refute that view as the final conclusion of the argument.
Example:
Manhattan Prep Question
hereP.S. It is easy to make difficult Boldface Questions using this pattern.
Weaken Questions
- If the stimulus mentions atleast one number (except for the Year Number), ratio, proportion, or percentage, the probability of a Statistical Flaw climbed past 0.5. For all those who are scared of Probability, it is calculated out of 1
- If the stimulus claims that a plan will succeed based upon historical/geographical evidence, the probability of a Generalization Flaw climbed past 0.5.
- The correct answer does not actually has to Pulverize the conclusion. An option is correct even if it produces little doubt about the accuracy of conclusion.
Strengthen Questions
- The correct answer would support the assumption or conclusion. Mostly in Easy Questions.
- The correct answer invalidates a possible weakness. Mostly in difficult questions.
Inference Questions
- Expect some play with the quantitative words such as Some, Many, Most, Not All, None, All, Frequently, Seldom, and so on. These words can be encountered both in stimulus and options.
Boldface Questions
- Many a times in Difficult questions, there are Either 2 conclusions - 1. Main conclusion. 2. The conclusion that works as a premise for the Main Conclusion OR 2 points of View and options try to confuse us in the word play.
P.S. This is all I could think off the top of my head. Feel free to comment with your inputs. And yes, I will add sample questions as I encounter them during practice henceforth.