At least 200 people reach this blog searching something related to sitelinks and reach this article : Getting sitelinks in Google search result or How to foster the emergence of SiteLinks in SERP.
Why people searches for Sitelinks or try to find some way to get Sitelinks?
Sitelinks are one of the most elegant features in Google search result page. Not all websites get Sitelinks and there are different appearance of Sitelinks too. Sitelinks appears from the automatic observation and analysis of Top Landing Pages of a domain.
We already have discussed almost everything about Sitelinks in the above mentioned articles.
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Here is the exact lines said by Google about Sitelinks :
We only show sitelinks for results when we think they’ll be useful to the user. If the structure of your site doesn’t allow our algorithms to find good sitelinks, or we don’t think that the sitelinks for your site are relevant for the user’s query, we won’t show them.
At the moment, sitelinks are automated. We’re always working to improve our sitelinks algorithms, and we may incorporate webmaster input in the future. There are best practices you can follow, however, to improve the quality of your sitelinks. For example, for your site’s internal links, make sure you use anchor text and alt text that’s informative, compact, and avoids repetition.
If you think that a sitelink URL is inappropriate or incorrect, you can demote it. Demoting a URL for a sitelink tells Google that you don’t consider this URL a good sitelink candidate for a specific page on your site. Google doesn’t guarantee that demoted URLs will never appear as a sitelink, but we do consider a demotion a strong hint that we’ll try to honor when generating sitelinks.
When the Sitelinks appear?
There is no time constrain. A very important website might get sitelinks within 2-3 months or less. There are some probable factors which influences them.
Type of Sitelinks ? What is that?
We have not found any document regarding Type of Sitelinks. It is our observation based.
This type of Sitelinks probably initially appears or for the websites with less content variation :

“Average” kind of sitelinks we had before:

Kind of “Mega” Sitelinks now :

“Giga” sitelinks with Search :

Conclusion
It seems that the “Mega” type is “standard” now. Also, Google clearly has said about having sitelinks algorithm. I read somewhere that using Google Custom Search helps to get the Site Search feature within the Sitelinks. Probably it is not fully correct. Microsoft uses Bing for their website!
