Make sure that the video company you select is a member of a professional organisation and comes recommended. If friends cant advise, your photographer may know of a reputable videographer.
Make sure you ask for references and see examples of other wedding videos the company has done.
Decide on the style of video you want. It can include every aspect of your wedding day from footage of you getting ready to the fireworks at the end of your reception or you can opt for something more simple that covers just the ceremony, speeches and first waltz.
Discuss the editing, music, title and length of video you require.
Make sure you enquire about your videographers equipment. It should have extensive zoom facility for unobtrusive shots at the ceremony venue, and also work in a wide range of lighting conditions.
Make sure you (or your videographer) check with person conducting the ceremony that videos are allowed in venue.
If you are having a soloist either playing or singing while you sign the register and it is important to you that it is captured on film, make sure you tell your videographer beforehand. The cameras microphone alone may not be adequate to pick up a quality sound recording.
Ask when you can expect to see the finished video after your wedding day.
As original footage will be far longer than finished video, remember to ask if it is still available just in case an important guest has been left out.