Yesterday I wanted to finally figure out the 3D focus tracking on the D3s. Since the D2h I've been using the single point with continuous servo - emphasis on "single point".
So last night I sat on the front street steps with the manual and got to it - as traffic would pass I chose my subjects. First a truck - some cars and then two Long Borders rode against traffic to the South - and the 3D tracking is a game changer.
The focus point jumps around and moves with the subject as you track - whoa!! I'm embarrassed I haven't been using this before.
Single point or 3D is easily available with the flip of a switch on the back of the camera. So I can easily switch between the two.
The point of all this - every once in a while break out the manual and learn more skills of your craft.