How to use testimonials (text, image, video) to increase conversion rates

Video Testimonials:
eDiets does a great job implementing a video testimonial AND focusing the user on the form. I love it! This one above is my favorite example of a landing page that makes effective use of a video & testimonial. I'd love to find out how much this video boosted form completion rates. Does anyone know? Check more examples after the jump.

Bubble Testimonial is a company that specializes in producing video testimonials that "pop!" on to your screen. You can see an example of the video testimonials on cool site of the day's landing page. This seems fairly simple to implement. I'd be interested in seeing if the addition of a video testimonial (such as this) can help increase conversion. 

Video Testimonial DON'Ts:

• Don't just link to a video file such as .wmv. I've come across this many times. No one wants to download a file and go through the hassle of open it up in realplayer, itunes, etc.
• Avoid directing users to a different page to play the video. Embed it. If you can't embed it, at least use a lightbox.

Image Testimonials

When I think of image testimonials, I think of before and after pics like what you see above. I think Diet sites in general do a good job with implementing image based testimonials. I guess it's hard to mess up since it's so relevant!

Below is another one from eDiets. This one is very clever and pretty. The image testimonial is part of the button to complete the form. Great way to address potential form anxiety.

Text Based Testimonials:

Use Testimonials to Relieve Anxiety & Friction points on Check out forms:

- Where to place:
Close proximity to anxiety inducing fields that ask for sensitive information (credit cards, reliability, personal info) ¹

- Consider Relevancy:
Put testimonials that are relevant to the anxiety. For example: Testimonials that address the smoothness of a transaction should be placed on the page where credit card info is entered. ¹

Testimonial Writing Tips:

1. Be Specific:
   
   • Example: Within 5 weeks, I started to notice a visible reduction of dimples in the fat around my stomach. My cellulite is steadily disappearing and I can't wait to flaunt my new body!
   • NOT: These guys are the best! A+++!
2. Address Skeptics
   
   • Example: "At first I was skeptical about XYZ product helping me reduce the pregnancy stretch marks. By Day 20 of using the product, I saw a huge difference. Even my husband noticed!"
3. Consider the Context
   
   • Landing Page: Put testimonials that urge the user to take the first step in filling out a form, clicking the submit button etc.
   • Check Out Page: Put testimonials about risk free returns, how great the outcome was etc to urge them to complete the process.

Third Party Testimonial Tools of Interest:

• IVouch:  Dynamically displays testimonials on your website.
• RatePoint: Captures, manages, and promotes real customer feedback and reviews
• Bubbletestimonial: Displays a floating video on your site
  
• Visit MarketingExperiments for the full study regarding text based testimonials