Meta Keywords tag is ignored for ranking factors by Google.
Title and Description are important. Title is very much a backbone factor
for onsite SEO. Descriptions are important because it's what is usually
used as the info displayed in the SERPs. Lacing the descrption with
keywords helps show relavancy as they show bolded in the SERPs.
I usually tell my clients it makes up 20%, but understand these are both
guesstimations. No one really knows for sure, but it's reasonable to assume
links make up for the majority of the calculation.
David Kyle