Google’s Spider crawls your site any time your site’s address is click able on other sites’ pages.
It is better for your site to be found by Google than you suggest your link to Google Add URL. If your site’s address can be found on other sites with a higher page rank, then those other sites assigns a little from them page rank to your site and then, Google think that your site became a reference more important and in this way Google will bring up your site’s page rank.

Sometimes your site might not be on Google's lists but this might happen because of a few things like:

1. your website hasn't multiple links to other sites
2. your site was launched early, and Google didn't started to crawl it
3. your site's web-desing doesn't respect the seo rules, and is difficult to google to crawl
4. your site has been offline for a while

In conclusion Google loves backlinks and if you want your site to be well ranked you should add links to other partners' sites. You can submit your site to Google Sitemap and they will know permanently about your website.