If you're serious about law school, I recommend this site:
http://www.lsac.org/AboutLSAC/about-lsac.asp
It can answer most (if not) all your questions about law school and the LSAT's.
Anyway, the scale is from 120-180. The average score is about 150, but you should score well over 160 to get into a good law school. A GPA would be anything at honors level, so a 3.4 at the lowest usually. There are, of course, exceptions to this. Law schools look more at the classes you took. They want to see you focus and do well on classes that emphasize reading, writing, and critical thinking. This is why you will find out, taking pre-law won't necessarily give you an advantage. People from all wakes of education attempt the LSAT's to get into law school. Dropping a class can affect your admissions, depending on the reasoning behind it. If you had a bad illness, it can be overlooked. If you simply couldnt pass the class because of your grades, that's not looked highly on.
You will get parts in the applications to explain certain situations.
