Example: Other day I commuted the “fallacy of four terms” and someone noted it and I immediately thanked them for it!
If you can find the argument is invalid, by not following a rule of inference or some type of deductive reasoning the argument is defeated. However, make sure they are not giving you an inductive argument, which can not be valid and only requires cogency where it is likely >50% cogent, but less than 100% cogency.
2) Look for reasons why the premises are not true (false) and try to give defeaters. I would say “not true” or “false” rather than “bad” because “bad” is a value judgement.