You could get best back links from article sties but it takes very much time to write and submit an article. Forums, blogs, directories are good platforms to get back links, however, it is useful to have some profile links too on social sites.
It depends on your capacity, but on an average 100 to 200 links are sufficient in forum posting , bookmarking, listing, and some quality links on high traffic sites is also necessary.
A back link is your that url on which you have hyperlinks and placed on other website. These back links are very useful for ranking and traffic on a website or its webpage. Links in signatures are called back links.
Your question is confusing whether you want know how to use google ads or how to submit your site to google. So you could take help of Adsense account for advertisement purposes and submit it your site by your google webmaster tools account.
Yes, you are right, we must follow google webmaster tools for enhancing user experience. The guideline provide information how some webmasters implement unethical methods of link building which should be avoided.
Because plastic bags take too much time to degenerate and they block sewerage pipes and pollute our environment. Plastic use also causes cancer according to some scientists so it is hazardous for our health.
Link building is a meticulous task whether it comes for internal link building or off page link building. You should not use unnecessary keywords that do not related to business. Use best keyword that depict your business information exactly and truly for better user experience.