how to make sitelink in google?

Your site has to be an authority for the choosen keyword. Therefore, you need strong backlinks, backlinks, backlinks.

Make DoFollow link and ping them. High Page Rank do follow site link index fast in search engine.

I also watch my sites links are in search result just after my site link which are in "Buzz Up". Links in Buzz Up have a good position in search result.

Put your post in google buzz. Seems to help a little bit.

What is this sitelink in google? how it works and helps seo activities? any concern is much appreciated.

I have Google Sitelinks (6 of them) on one of my PR3 sites.

Getting site-links to show in the SERPS is pretty easy with the method I use but if your working on an existing site restructuring may take some time depending on how large it is. Site-links come from having a good navigation structure, but specifically having good navigation in the eyes of Google's bot by "siloing" your site structure. EDIT: This doesn't mean that you need silos to get site-links, its just a method that works very well. Silos give Google a clear and distinct layout of your site's content allowing it to show specific categories in the SERPS.

There are two types of silo setups, virtual and directory based. A virtual silo is basically an internal linking structure where your site is broken up into themed mini-sites within itself through the use of categories. The key is to only link content pages within a category to other pages within the same category, the home page, and other top level categories. Never link sub pages of one category to a sub page of another category or you will loosen up the theme of each category. You want tight silos to have your site-links listed in the SERPS.

A directory based silo separates each category into mini-sites through the use of sub directories on your site. For example, if you had a site about sofas, all pages regarding leather sofas would be in the "leather" directory like:
sofas.com/leather/black-leather-sofas.html
All pages about suede sofas would be in there own directory as well, like:
sofas.com/suede/brown-suede-sofas.html

This tight siloing lets Google know exactly what your site is about, how your site is structured, and gives the bot a very specific path to follow when crawling your site. You can use either virtual or directory siloing but I prefer virtual because I work with WordPress which makes category siloing a little cumbersome. Plus with a virtual silo all your content pages get to stay right next to the .com rather than within a sub directory.

You'll know that you have a good silo set up when you Google YourDomain.com and the site-links are visible. The top level categories of your silos will become your site-links in the SERPS. The site-links won't show up for every keyword that you rank for, usually only keywords that your seen as an authority on by the Google, but it should always show up when you search for your domain if you've achieved it. Its pretty easy to do if you keep your silos (your themes) very tight by using little or no cross category sub page linking and have enough themed content on your site to justify having multiple categories. Do an image search for "website silo" and you will find some good diagrams which illustrate the concept.

You don't need a silo structured site!

I have Google Sitelinks on a blogspot site...