Youtube embeddingTo embed youtube videos, for those of you who didn't know, you need to put the link to the video between [youtube] and [/youtube] tags.
HOWEVER
It can't be any old link you copy from the address bar because of the many variations youtube has in it's links (as far as I can tell, most of them are to find out if you found it by following an embedded clip from somewhere, or got it from the related bar on the side and so on. Harmless data gathering, but not fun for anything that demands order in it's links, like this forum's embed system (and youtube's own embed system, for that matter).
URLs 101This is the URL format expected by the [youtube] tags:
https://www.youtube.com/watch?v=FzrNfOX9fTs#!This points to the same clip, but is wrong and will result in an ugly failed bit of text in your post:
https://www.youtube.com/watch?feature=player_embedded&v=FzrNfOX9fTs#!Now then. The question mark and the ampersand (&) are key here. These separate what's known as "GET parameters", parameters used by the website, passed in the url.
The question mark denotes the first parameter and all the following ones are separated by an '&' instead. The part in front of the = sign is the name of the parameter, the part behind is the value. The value can change to give different results on the page.
To give you an idea of how this works, you can sometimes see things like '?lang=en' on the end of a URL, meaning the current selected language is English. If the website supports it, you can change this to, for instance, '?lang=fr' for French.
Putting it all togetherI hope you can see the connection in the youtube URL now. '?v=[ID]' sets the unique video ID for the clip you want to watch/embed, and you will find this in any type of youtube URL that points to a clip, no matter how many other parameters could be in there as well.
To use our original example again, I highlighted the part you're looking for
https://www.youtube.com/watch?feature=player_embedded&v=FzrNfOX9fTs#!Once you've found the parameter you need, you can delete everything else that's still behind the question mark, except that bit, and that should leave you with a nice and standardised "https://www.youtube.com/watch?v=FzrNfOX9fTs#!"