Help : Using 7D for video / focus issues

[superNoid]

Perhaps its just me being a complete noob when it comes to DSLR video but I"m having trouble understanding how to get around focus issues, limitations with this setup. Prior to my 7D all my video was shot on a Canon Vixia HF10, handheld 1080p camera. Its works, but its very limited. One thing I never had to do was ever deal with focus.

Now obviously with a DLSR, say my 7D with my 24-70 2.8L I have so much more potential. Problem is, I do not know how to unlock it. My biggest hurdle is dealing with having anything I shoot in focus. I know that there is no real auto focus when filming, or that when you use it, its slow, visible and thus should not be used. So I gathered that using manual focus is the way to go, and I'm fine with that. I'm fine with a learning curve and new tricks.

What I dont understand is manual focus and video shooting 101. I was at a wedding and their videographer was shooting with a 5D and what looked like a prime lens. It got me thinking, with adjustable focal length lens like my 24-70, should I be setting it as close to 50mm, then manually setting a focus point on a reasonable distance and leave it alone? I saw this videographer filming away, moving all around the room and never adjusting focus.. the way I'm shooting today I could never do that.

Everything I film is out of focus. Say before I start filming I focus on an object that is X distance from the camera. Cool its in focus, as I walk around and film it just seems like everything is out of focus unless I stand a certain distance from that invisible focal length.. its really hit or miss.

Ultimately I feel I just simply do not understand how to shoot manual focus video with a DSLR. Is there some 101 type steps I'm over looking? I'd love to just focus on something, start filming and have the majority of what I then film as I move around a room be in focus. I have so many ideas for film and I'm dying to get amazing quality from my 7D and L glass.. Help me CDP .. you're my only hope.

Help?

ps. Lay it on me, I can take brutal honesty.