if yo're using firefox, install this firefox plugin and it'll do the work for you. http://tools.seobook.com/firefox/seo-for-firefox.html
Firstly you can take help from seo tool. And Secondly you can check difference from source code of web page. If URL on anchor tag in simple then dofollow either URL with no follow tag then this is nofollow...
I use seo quake and it is very helpful for me to tell the bio data of a hyper link. i.e do follow or no follow