First I go off enjoyment (base ranking), then I go of quality of the anime. Even if i enjoy a shows a bit more, if the quality is way better (for me) is better for the other, i would have the quality higher. Quality means animation, story, etc. Quality also depends on my mood.
Priority shows if its a high, medium or low score. Some shows have two numbers/scores (in tags) this means very close to a rank up/down.
Enjoyment/base ranking system
10: Haven't seen a perfect anime yet, so my 10's are either really high 9's or have a special place in my heart/my favourites. (Mostly the first anime shows i've watched).
9: Want to re-watch the whole series or have
8: A great show but not something i'll re-watch, or just missing in a few aspects compared to a 9
7: Had great moments but on average was just fine
6: I got bored watching it, but still enjoyable
5: Why did I watch this
4 or Lower: Either hate it or dropped it cause i was bored. If I drop a show doesn't mean I hate it, just means i couldn't binge and i'll come back to it. I normally not in the mood to binge so I just drop it. But i will finish off at a latter time.
I rank off-brand anime as 7 being the best, due to not wanting to many of them high on my list.