Currently, a site is showing 7 links when I Google link:www.sitename.com Can anyone suggest how to increase this number?
Just get more and more backlinks, google will crawl them and add it to the index. Usually within 1-3 months, again depends on the site from which you are getting backlinks, what is their PR and how often google crawls them
Yes it seems that Google displays only the strongest links to your site, but it is possible that even if you get a lot of decent links after 3 month you will not see any changes while using Google link command, so my advice is to forget about it. It is not important at all.
@ Greg Carnegie At yahoo it is showing nearly 14,000 back links. I am trying hard to add more and more quality links. Let us see how it works.
Are the pages of the site getting indexed by the Search Engines? Internal pages with PR should also help increase the number of links to a site on Google, when you check using the link: command. Just keep working on getting links for the site, do directory submissions, article submissions, add a link to it in your sig etc and you should see them increase in the next update.
To increase Google back links submit your site to a quality directory link to a related quality site create a unique quality content.