From time to time, people announce papers claiming to have settled long open problems like $P$ vs. $NP$. There have been many attempts, reading them is time-consuming, and finding bugs in their arguments is not easy, ... . This brings up the following question:
When would you read a paper claiming to have settled a famous long open problem like $P$ vs. $NP$? What are your criteria to consider such an announcement as serious?
EDIT: I am mostly interested in the case that the paper is in your area and is not written by a crank but by a mathematician with previous publications in reputable journals (although not necessary in the same area or a related one).