First you need to find a video that you want to use. ;-) Not all Youtube videos are embeddable and many copyrighted ones are not. If that is the case, you'll need to just link to them.
Get the code from Youtube
If you're looking at the main user channel, you may not see the embed links, but you can get to them in a number of ways.
Underneath each of the videos posted on the channel, is a tab/button which says Info. Click on Info and you will see
View comments, related videos, and more
Click on this get to the video with its embeddable info.
The Embed box holds the code for the embeddable video. If you look carefully in the Embed box, you can usually see what the size is -- object width is the width that the embeddable video will be.
If the pre-configured options will work, you can skip customizing the code; just grab a copy (Ctrl + A) of the code from the Embed box. You'll be ready for the blogger section then.
To customize the embeddable video:
Click on the tiny star icon (whoa, is that easy to miss!). Clicking on this will show you the different pre-configured sizes for an embedded video including size and color for the player.
Below the Embed box you will now see a bunch of options to configure your players.
Note: Include related videos may or may not include videos from the same user or necessarily on the same topic. If you want to create a group of videos, your better bet is to make a playlist, which can then be embedded.
In the Embed box, you will hit Ctrl + A (or right click Select All, if you have that functionality).
Embedding a video into a Blogger post
For Blogger (blogspot blogs) you MUST switch to the Edit Html button in order to embed the video. In any other blog service or product, you will need to somehow get to the html, unless you have embed Youtube functionality.
Find a spot in your post where you want to add your video.
Now hit Ctrl + P (paste) or right click paste if you have that functionality.
It will paste in something that looks
like this. Recognize that stuff? It is
indeed, the code from Youtube.
If you click on Compose, you will not see the video.Don't worry, the code is still there and if you click Edit Html you will see the code.
If for some reason, you need to edit the width and height even more you can do it by tweaking the height and width even more, directly in the code.
..and that's how to do it (or at least, one way to do it). I realize this question has probably been answered alot over the 'net, but it was a question asked to me, so there you go!
If you do it right, you'll get something like this... yes, I am in this movie... LOL