Just like a photographer, choosing a videographer is just as important. Make sure you do your homework before settling by looking at their work, style, and skill and if you feel comfortable with them.
Picking the Videographer and the Cost
As with any vendor, find out what is included in the videographer's package, like the burning of DVDs and how many DVDs are included. Find out if the videographer uses an assistant, because that will have an obvious cost impact but might make a difference to you . . . both in the sense that the videographer's set-up may be more efficient, and also that it's another body to have present (and if they are working the reception, possibly feeding as well).
To find a videographer from scratch, use a reputable source, such as the Nationwide Directory of Event Video Professionals, and don't forget online review sites like Yelp and wedding websites as a source, too. If your venue offers a videographer in their package, that's great. But be sure you can view their work and meet the person, just the same as if you were hiring an outside vendor. (And also because the venue might be charging more because they can.)
It may be tempting to have a guest film the event, but just remember that they'll be working rather than enjoying the wedding, and from a professional, you can expect fancy stuff like DVD menus, extras, and great editing. You also have recourse if it doesn't turn out how you expected.
Be clear about your expectations! Meet with them in person to get a feel for their professionalism, and if it's important to you, be clear about what you want them to wear, etc.
Style and the Finished Video
In fact, let's talk about style. Think about what you want before you meet with anyone, because that will be a big factor. If you want video that's chronicling the event, but not necessarily with close-ups and high editorial input, then that's easier to find and your videographer may be less of a distraction. But on the flip side, if you want a more involved video and close attention to detail, be prepared to look (and pay) more for skill and accept that your videographer may be distracting from the actual action at the wedding to your live audience.
Also, decide which events you want your videographer to attend — maybe you just want the ceremony on film, and maybe you want the whole shebang — rehearsal, preceremony preparation, and reception. This will have an effect both on the content of the finished video and a big impact on cost. If you can't pass up video to really relive the wedding but are on a budget, consider having only your ceremony filmed.
Ask about lighting — ensure they'll have enough at each site you'll have filmed, and possibly have them visit your sites and tell them what you're thinking in terms of the overall lighting.