Here is a page describing the YouTube Embedded Player Parameters.  These parameters are query parameters you can add to the end of the YouTube URL.

There are different parameters you can add to the object and embed statements.  Here is an example.

<object width="320" height="265">
 <param name="movie" value="http://www.youtube.com/v/6sHenGpeGgo&hl=en&fs=1&autoplay=1"></param>
 <param name="allowFullScreen" value="true"></param>
 <param name="allowscriptaccess" value="always"></param
 <param name="wmode" value="transparent"></param>
 <embed src="http://www.youtube.com/v/6sHenGpeGgo&hl=en&fs=1&autoplay=1" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" wmode="transparent" width="320" height="265"></embed>
</object>