I use the entire spectrum from 1 - 10. I do not give horrible shows a "5" like a lot of people do, but I would actually give it a 1 - 3.
I always rate anime based on their theme, for instance if I am watching a Comedy anime, while I will look at all its aspects such as characters, music, etc. I will mainly be rating it based on its jokes and so forth.
One of the most important aspects for me in an anime is the dialogue. If I feel like the dialogue makes no sense, or is broken, I will most likely instantly drop an anime, and seeing an anime with horrible dialogue also tends to make me want to give it a lower rating.
I hope you will agree with my way of reviewing things, and I hope you will find an anime you will enjoy watching from my list!