Getting a Site Out of Sandbox?

As far as Google is concerned not all sandbox invites are equal. Certain factors will determine the length of your stay in the Google sandbox. If the keywords your website is targeting are highly competitive then your website will be quarantined for longer. irrespective of factors such as good on-page optimization, incoming back links and original content, the average duration in the Google sandbox is 3 months. But doing the following has been observed to shorten a site’s duration in the Google sandbox:
* Register your domain name for more than one year
* Upload your site for live viewing as soon as possible
* Maintain excellent-practice seo-linking campaigns .

Just do usual SEO work and your site will get out of the Sandbox when Google decised that it's time for it to leave it.

I think you would get your sites our of sandbox earlier by building backlinks from high PR sources on your niche.

Have a nice day,