What are Google Sitelinks ?
Sitelinks are basically additional links to your website from the Google results page. These links appear below your main listing and link to some of the key pages of your website. Google’s algorithm will randomly choose the links and the quantity of links it displays.

Here is an example of you search for ‘bbc’ on Google UK.
These sitelinks generally only appear if you search for brandnames rather than services.
Other searches that display sitelinks include
How do I get Sitelinks ?
Unfortunatley there is no definate way of generating these additional links. There are certain points which seem to be taken in to account before sites can be awarded these though. These include
If your website meets the above then Google may assign your website with Sitelinks.
Conclusion
Sitelinks can be a really nice addition to your websites results on Google however I must point out the following.
Sitelinks usually won’t appear for searches that consist of two to four words. These words are the most important keywords for website promotion and search engine optimisation.
A Beginners Guide to the Google Link Algorithm Part.1
EVERY search engines primary goal is to provide the best quality, most relevant search results possible and the way each search engine does this varies considerably.
Using Google for Keyword Research
Did you know that you can use Google's keyword research tool which suggests keywords "related" to the term/phrase you enter.