How to auto focus in video mode on a nikon d90?

How do i focus in video mode on my d90 without rotating the ring?

I'm a Canon guy but I would bet you don't. Only a few newer dslr cameras have auto focus in video.
Besides, you need to learn how to do manual focus and two, auto focus is a sham and you don't want it. Trust me I know. I own a camera with auto focus in video and it's the worst thing that ever happened to consumer level video. Why do you think not a single professional uses auto focus, it's trash in video… You don't want it.

The D90 was the first DSLR to have video mode, and consequently, it does not autofocus. However, any dslr owner should be adept at manual focus, so it is really not that big a deal.

You focus before shooting (auto focus works before shooting in live view mode), then manually focus while recording. Only Nikon's newer cameras have full time-servo AF (AF-F) mode.AF-F mode is prone to focus pumping, so not very useful. Better to manually focus during shooting if you need to.

The D90 doesn't have auto focus in video mode. Newer Nikon DSLR's have have an AF-F mode in video mode which is similar to how camcorders work but nowhere as effective or quiet. I think the D90 might have an AF-A mode but its not available in video mode.

With DSLR's you hear the AF motor in the lens or the body constantly working which stinks for video. Your best bet is to just leave the camera in manual focus mode. Any time I shoot video with my D5100 or D7000 I just leave the body in manual focus mode.

EDIT: I found this review of the D90 that just focuses on the D90's video's capability's.

http://www.luminous-landscape.com/reviews/cameras/d90.shtml