[support] How to extend the factors of content ranking?

Hi! What would be the best way to extend the factors of content ranking in drupals search by the (numeric) value of a specific field in a content type? E.g. I have a content type with a field 'rating' which takes values from 1 to 4. I want to see entities with a rating of 4 on top of the search results and the rest in descending order of the field 'rating'. Thanks in advance, Alex