You will need to have quite a bit of traffic to your site to get those. Keep creating great content. Google will not give those out easy.
Be sure that you have your navigation marked up with semantic HTML and include an id of
navigation on your menu. This will help Google know what links are your navigation. (as opposed to a list of links).
Also, once you get them Google will give you an option to control what links you want in your sitelinks via Google Webmaster Tools.
There is no easy way or publicly know algorithm that will give you sitelinks. And I'm sure that algorithm changes all the time.
- Don't think about it too much and give it time, sitelinks are rare.