I do not use any fancy, 12-point score sheet. My star rating system is the same as the official Goodreads system (the stuff that shows up if you hover over the stars).
And here's the breakdown, brought to you by the 10th Doctor and Doug:
1 star = Didn't like.
2 stars = It was okay.
3 stars = I liked it.
4 stars = I really liked it.
5 stars (the holy grail) = I loved it!
Image sources: 1; 2; 3; 4; 5