UPSC has released the list of common mistakes. At least after this PPT converted to PDF, people should not make it.
Here is the link
https://upsc.gov.in/sites/default/files/Common_Mistake_OMR_SAL.pdf
DOUBT:
In worst case scenario, by mistake if we bubble 25% of a wrong answer, and leave it as it is: Then it would be counted as 0 marks or Negative marks?@Neyawn
