[dharmon]

This is a good article at covering various business metrics, but I just have two things to add:

1) Relative valuations can be slippery, and I personally sleep better when I make an investment I am comfortable with on an absolute basis.

2) Most often, success in investments is more dependent on the accuracy of your judgment of the business at hand than on your ability to wield spreadsheets. If you are good at the former, you can be middling at the latter and do well, but generally not vice versa.