Watch a sample video. A video is worth a thousand words. See if it looks like it was thrown together like a cookie cutter or if special attention was performed. Look for unique shots and angles. Most wedding videos look pretty similiar. The ones at the top of the craft use special equipment like cranes for dramatic moving shots like you see in Hollywood. The big guys also make special graphics and video color/filter/transitions and sometimes even 3D animation effects to enhance and set the wedding in a league of it's own. Listen to the audio to see if it was also professionally mixed. Most co-called videographers don't use multiple pro-mics and professionally mix audio in post. See if they have ever done any high-end commercial work. The best wedding videographers take the high-end commercial equipment, software and skills and blend it with emotion and elegance to create the best wedding cinematography. And perhaps most importantly, does the video have emotion? Does it convey the feeling on screen that you have in your hearts?