I and 100 others second the recommendation to read OKtrends: simple, frank statistical analysis. It's not the most useful information, but I was really surprised at their frankness when discussing touchy subjects: religion, race, attractiveness. They're very down-to-Earth in their analysis.

Also a bit about what people are looking for dating wise would be useful. Generally that is too dull to put in the profile itself, but required for advice I think.

Good point.