First you have to search in Google with your relevant keyword and find the related sites. Eg - My site is http://tour.bizhat.com and I am using 'travel to India' as a keyword. Get the mailing address of webmasters of the related sites and contact them via mail requesting for link exhange.

Inform them that you have already added their link and like to get a link in their site. If you are lucky, you will get a link. You can wait for a month for the link and if not remove the link from your site. Related links will count a lot and your site will be ranked high by search engines.