“Whether something is interesting or not is a matter of how you look at it.”
I rate base on how interesting and enjoyable the series or movie. If it has a unique story and good storytelling, or if it makes me laugh in almost every episode, or it left a good impact on me, or it makes me amaze, I will gave that a high rating (7-10). If it didn't suit my taste I will just drop it 'coz I don't want to waste time on something I will not enjoy. Though I will try to avoid rating it because I know some will still find it amazing and worth to watch. But if I happen to give it a low rating is because it's just I find it ridiculous and not recommended.
I don't have any particular genre but so far I've been watching psychological-thriller, mystery, action, comedy, romance and slice of life. I have a roulette in my phone with list of anime I planned to watch which I used to decide which will I watch next :)