Interesting question. First for me is plot description, it has to sound interesting or appealing. Second would be genre - I tend to search for shows that way. Another factor is buzz and word of mouth. If the buzz lasts long enough, I'll watch something that normally wouldn't appeal. Game of Thrones and Squid Game are two examples of that. Sometimes a star, writer, or showrunner might be a factor; I will definitely give any Lindelof show a try on the basis of what he's done.

I'll try an episode, but if it bores me or turns me off, I may not even make it to the end. I do rewatch shows, though.