For traditionally published books, it's usually the word of mouth, and optional, or third-party site reviews.
The covers are irrelevant for traditionally published novels, the author probably had a little to no say in it, and was done by the marketing department which didn't read the book. Unless there is some immediate turn off, I ignore the cover.
Titles doesn't mean much, other to have something to google it by...
For the amateur books like we could find here, the cover usually is what the author wanted, or close to it.
It is usually covers that still look recognizable on the thumbnail that gets my attention. If it is too blurred, I skip the book.
For the amateur book I could search by tags (assuming I know what the tags are, the SH had a lot of them, and it is far from an only site with too many sites). They tend to be helpful, and you could start reading for free, so investigation is not required.
I usually ignore the impossibly long, weird titles like "That time the Moderator John reincarnated as the first hokage of the hidden censor village" or whatever ... (unless I specifically look for translations of some Japanese or Korean novel). This naming convention rarely bides well for western originals.