htmlbasictutor - 8:08 am on Jan 17, 2012 (gmt 0)
You can't. <wink>
All you can do is write the best meta description you can and hope it suits the person's search.
Google and the other search engines will display what they think best suits the user's search.
More info here at Google: support.google.com/webmasters/bin/answer.py?hl=en&answer=35624