Google Sitelinks are the collection of links that appear under some search results. These shortcuts are meant to help users navigate your website. Sitelinks are only shown if Google think they will be of use to the viewer and are relevant to the users search query.
Google’s algorithm chooses uses your sites structure to choose which sitelinks to show. You can’t choose which links are visible but you can choose to block links using Webmaster Tools if you think they are inappropriate.
Once you’ve blocked a Sitelink it won’t show in search results for a period of 90 days. Bear in mind that Google only displays Sitelinks from a site if at least three are available. If you only have three and you block one then no Sitelinks will appear at all for your domain.
Factors Which May Trigger Sitelinks
1, Ranking at number one for a given keyword.
2, Domain age. Older domains are more likely to receive Sitelinks.
3, Well structured, easily spiderable navigation.
4, Having good quality backlinks.
5, High natural search traffic.
6, High click through rates from SERPs.
7, Appropriate outbound links.
There is no way of influencing Google into giving your website Sitelinks however if the above factors are in place then your website stands a better chance of receiving them.