what are the Effective external links?

i have one question ..

i build one robots.txt on my website

nofollow /?

i hope to block the search energine to get some page like www.digitalpoint.com/?action=thisiswhat

the question is:

i have built some external links such as www.digitalpoint.com/?action=thissiwhat

do all the external links become unuseful becuase of my robots.txt?

 

I heard external link to trusted, on topic sites helps to show relevancy....