When scrolling through the thumbnail lists, it'll obviously be the thumbnail. I'm not too picky, generally a icon with the characters is what a prefer to words on a random backdrop photo image. Even logos are more of a tough sell for me. but if it's a novel that is using re-uploading game/anime/manga art then I am staying the **** away from that shit.
After clicking I'll read the summery, if it sounds interesting I'll give it a try, if not I won't. I don't have time to read through something I might not like in the hope of being 'pleasantly surprised'
Read the first chapter or few pages, if I dislike it, I'll stop, if I like it, I'll keep reading, if I'm not sure I'll read more to see if I like or dislike it, if I still can't figure out if I like it after the first 2 or 3 chapters it's pretty clear the story isn't clicking for me and I'm not going to be able to really get into it.