Someday I wish Google would be straight forward and say if your site is in the sandbox, and why sites get put in the sandbox. SERIOUSLY GOOGLE! What’s the worse that can happen if you use a little honesty in the matter? Until then I use a special trick to keep/get my sites out of the sandbox.
The trick rides off one principal which my own sites’ history has proven to me to be true. Google will almost never put a new domain from an old site in the sandbox.
Therefore to keep out of the sandbox you need to trick Google into thinking your site is from an old domain. You already know I like to keep old domains and websites around even if they don’t make any money. This is one of those times your going to need them again.
Find an old site of yours that gets crawled regularly. Create a subdomain. Mirror the main page of your site on the subdomain. Wait for it to get crawled and indexed. Then put a 301 redirect to your real domain. This will make Google realize that your site which is relatively new is actually an old site that got moved to it’s own domain.
Out of the sandbox you go!
Keep this in mind for your next website project. I have found it doesn’t hurt to plan early and release both at the same time. Then you just have to wait a month or so and put up the 301 redirect.
note: I have only tested this theory four times in the past with four different websites of mine. It did work each time. One of the times I used it to get a site out of the sandbox. I cannot guarantee you that it’s perfect or that it will work for you. Please let me know if it works or fails for you because at this point I still consider it a theory.