I think that depends preety much on what you want to achieve.

Is it a single asp.Net application that you are developing or a set of different apps that would use the same database?

Here there is an answer I pretty much agree with. Separate schema and one database for one app/database. Two databases kind of beat the point of separation but three databases might be a better solution if the authorization rules remain the same.

As for the DB first approach there is a pretty good article (and code) here.

I think that depends preety much on what you want to achieve.

Is it a single asp.Net application that you are developing or a set of different apps that would use the same database?

Here there is an answer I pretty much agree with. Separate schema and one database for one app/database. Two databases kind of beat the point of separation but three databases might be a better solution if the authorization rules remain the same.

As for the DB first approach there is a pretty good article (and code) here.