I could well be teaching my grandmother to suck eggs but here goes. 

If you are at a show and you want someone to record your round I'm assuming that you and your dog know the person well or they are a member of the family.  What I would advise is to give them the camcorder already set up to record, but don't walk to the ring or queue up with them.  That way your dog won't start looking for your friend or relative if you suddenly go off into the ring and leave them standing just outside.

Don't let your friend or relative stand in a place that's going to be highly visible to you and your dog as you're doing your round.  I've seen more than one dog scoot off to say hello when they should have been completing their round.

The person who's filming shouldn't zoom in too close to you and your dog.  You need to be able to see the obstacles ahead of you on the film so that you can get the whole picture.  If you zoom in too close and all you can see is your dog going the wrong way you won't have clue what happened.  Did you make a mistake or was there a distraction?

Ask the person who's filming to start the camera rolling well before you start and leave it going until you're out of the ring.  Bernie has an annoying habit of missing the beginnings of my rounds and I can't train him out of it.  Perhaps you'll have better luck.

If you're setting up the camcorder at home make sure it's in a place where the dog can't knock it over.  Make sure it's actually recording beofre you go off and do your training and have a look through the viewfinder or at the LCD screen to make sure that your training are is in shot.

Replay your clips several times so that you can see and analyse exactly what you're doing. 

Share them on Youtube so that we can all have a look too!

Good luck