SEM is about several online strategies that promote WebPages. By marketing with the arts of paid placement, contextual ads, and paid inclusion; SEM is used to gain relevance on the search engines. The ranking of a website increases in visibility on the search engine result pages. Something most marketers do is to hire a third part professional to pull keywords and implement marketing strategy. The formula that is best for your SEM needs is so different from anything else in website design normally, but those who are experienced in it are eagerly sought after. The biggest issue currently hanging over the heads of most users creating and promoting content online today is plagiarism. SEM is actually more art than science. It is the combination of forces generated through public relations and the power of advertising. Duplicate content, redirects of WebPages, and regular updating are things to avoid if wring for an SEM company.

http://digitalmarketinginstitute.co.uk/resources/seo-interview-with-dan-petrovich/