Google Sandbox is applied on new websites, it determines the timing of site inclusion as well as ranking in Google search engine results (SERPS).
This process could take up to 6-8 months, which could be against your plans causing frustration to webmasters.
Do not waste time on checking your website listings in results page instead emphasize on SEO methods to accelerate your listings & improve status of ranking results.
Also make efforts to appear on other major search engines such as MSN & Yahoo since they do not have sandbox like Google, this will help drive traffic to your website while waiting for Googlebot to index your pages.
Link building strategy is another important issue not only will it improve ranking but also it will help Googlebot spider to find your pages easier while it’s in the sandbox instead of repeatedly submitting your website every time.
Content is king
Main part for ongoing development of your website is to add new content on continuous basis since the most thing search engines are after is good quality websites with relevant content.
Conclusion at the end is that waiting for Google Sandbox is nothing but a waste of your precious time; instead do some useful efforts on developing your website with relevant content & adding inbound links as a part of your linking strategy to make Google happy with what it sees as well as your target visitor.