I add a story to my favourites if I want to read it again, its that simple, also sometimes I add a story that I am partway through for easy access next time I visit but those are removed afterwards unless they become "true" favourites. There are plenty of stories and serials on here that I have enjoyed but only around a dozen (so far, I still have lots left to read) that I actually want to keep going back to over and over again. Obviously its a matter of personal taste, I like well-written stories but the writing styles and story themes of my favourites can vary dramatically, they do all tend to be mainly M/f though and some of them I like because they are good stories (such as Kira) and not just for the spanking content, others I like for particular scenes in them. I particularly enjoy historical and fantasy spanking fiction as these themes allow for harsher "punishments" (although I dislike anything I consider abusive rather than erotic, and by that I mean erotic to me not the fictional recipient) without sounding too far-fetched. There is a tendency amongst some spanking authors to either overstate the results of "punishment" or to understate it, I dislike both, for me accuracy and authenticity are preferable.
I do like to leave comments on stories I have particularly liked, whether I add them to my favourites or not, I would say that is maybe a better indication of how many people really like a story (bearing in mind that not everyone bothers to leave comments) than how many have it marked as a favourite
