I've been thinking about using youtube clips on my website, mainly for product reviews. Is this okay to do or would I be breaching copyright with whoever created the clip? Alternatively, do I just need to reference the user when I embed the clip on my website, such as placing them in the caption for the video?
It depends on the type of license that youtube video has (eg standard license or creative common license) and u need to link back its original author. As far as you don't take credit for that video its fair to use it.
Also, you have to ensure the uploaders of the video know that you would like to use it on their website. I guess if it's a commercial type video, then it should be ok for you to link to it