The feature to embed or play Youtube videos from a certain timestamp has been introduce long back but very few of us actually know how to do it. Suppose you have embed a video to your site but you want your visitors to start watching that video (start playing) at 2min, 10 sec mark. All you need to do is add #t=2m10s
at the end of the embed URL.
Check out the below video which starts from the 1 min, 9 sec mark. All I did was added #t=1m9s at the end of the video URL
This trick comes handy when you specifically want to refer to a particular part of the video and let people skip the unwanted part.