Hi all,
This is my first post, but I'm far from a newbie. How do I select the D90 Focus Point I want, and make it stay there? I'm in AF-S mode.

Example: I want to focus on a flower towards the left of the frame, and Not on the distant trees at the right. I know I'm supposed to hold a button down, and utilize the rear thumb dial wheel, and it's not working. Thanks...