Basically, for each video you found on YouTube for which you want to embed it in your blog or your website, look for the "Embed" entry in the right part of the video. There you'll find a string similar to
<object width="425" height="350"><param name="movie" value="http://www.youtube.com/v/kkT7A3jegBc"></param><param name="wmode" value="transparent"></param><embed src="http://www.youtube.com/v/kkT7A3jegBc" type="application/x-shockwave-flash" wmode="transparent" width="425" height="350"></embed></object>
and this is how it looks in your website:
Note you can change the size of the video accordingly. Just replace the width and height attributes in the HTML code above. Here's a smaller version:
