The good news is, this is very easy to do just by making a small edit to the URL.

Here’s what we’ll use as the example video.  This video talks about reconsideration requests in Google’s Webmaster Tools area:

http://www.youtube.com/watch?v=ntJhrM7CU5I

But let’s say that I only want to point viewers to a certain spot in that video, which starts to talk about how to gather further information in the Google Webmaster Tools area.  This is about 36 seconds into the video.

In this case I would just add the following to the end of the URL:  #t=0m36s

You’ll need to add the #t= and then add the number of minutes (in my case 0 minutes) and then the number of seconds (I chose 36 seconds into the video).

If I wanted to instead link to the 2 minute 12 second portion I’d then add to the URL #t=2m12s.

So here’s that link again with the point in time that I want to link to.  If you click on the link you’ll see that you’re immediately taken to that spot in the video.

http://www.youtube.com/watch?v=ntJhrM7CU5I#t=0m36s

This is a great help to those who only want to reference certain points in long videos without making their viewer sit and wait for the entire video.