I go a little more in-depth on my ratings in my lists. Here's a little guideline on those ratings to the RYM system:

5 Stars = 9.5 - 10.0
4.5 Stars = 9.0 - 9.4
4 Stars = 8.0 - 8.9
3.5 Stars = 7.0 - 7.9
3 Stars = 6.0 - 6.9
2.5 Stars = 5.0 - 5.9
2 Stars = 4.0 - 4.9
1.5 Stars = 3.0 - 3.9
1 Star = 2.9 - 2.9
.5 Star = 0.0 - 1.9

What each category means in my list ratings:
Lyrics = Strength of all lyrics
Vocals = Strength of all vocals
Music = Strength of the rest of the music and originality
Continuity = How well the songs fit together to make one solid piece of art. Bad track placement and poor variety hurt this area.
Longevity = Must have had the album for a minimum of 2 months and the rating is based on how frequently the album is spun afterwards. This rating fluctuates often and is the harshest of them all.