Recently I had to remove the old flange from the bathroom floor. It was rusted and broken in a spot, so it wouldn't seal... even with a new wax ring. The concrete holding the flange down was also bad.

What do I need to do? Put in some new concrete? Also... is there any recommendation for what type of flange I need to use?

It would be great if you could post photo of your situation...

There is several ways to go about installing closet ring in your situation. If you post a pic, we will be able to get right to the point w/o exploring long list of options.