My site is 4 years old and has got a page rank of 2 , Im updating content and the content is perfectly written by me and I have not copied from any sources but unfortunately even it caches as soon as the new page is published it stays up to a maximum of 4 days and then goes inside sandbox every 9 out of 10 pages goes into sandbox after 4 days. I want to avoid it. As soon as I create a webpage what are the things i should do to make the new page to stay longer (at least away from supplemental results) and compete with search results.
First you should bookmark that page after you created it in digg, delicious, etc. Then put some links to that page from different resources like blogs, forums, articles, press releases. After Google finds these links it will put your page in main index and give it some rank for the keywords in it.