Others call it Search Engine Optimization. The conclusion is that we can optimize search engines. Because we cannot do this, it really means Web Page Optimization. We can only optimize our own web pages in order to get higher search engine rankings.
I don't care what you have read, if your optimization tactics are in breach of the Google Webmaster Guidelines, or other Search Engine rules, any success you may be getting is only temporary. Don't take my word on this, read the Google facts before wasting your valuable time and money.
The Google Florida Update has seen thousands of high ranking pages lose their ranking or disappear altogether. What this means is that if we are not following the rules, we can see our pages disappear from the top results.
There are several theories about the Google Florida Update and what really happened. In my opinion, it is an attempt to filter out irrelevant search results, but it has not totally been successful. Here's an example:
While searching the term free roulette game at Google, I did not find a nice little shareware roulette game that I could play on my PC offline. The results are still cluttered with affiliate casino links. Compare this with the term free chess game and you'll see what I mean.
If you are thinking about buying SEO services, maybe you should read Google's article about Search Engine Optimizers. You will see clearly who you should hire and who to avoid. You will also see some tips on what not to do yourself if you are doing your own SEO work.
In my opinion, it is best to do your own SEO work, and the best SEO strategy seems to be not breaking the rules.
The mistake people make is to assume that search engines are stupid, so they go off doing the latest greatest Black Hat SEO strategy which sooner or later gets filtered out of the search engine algorithm. This is building a web site on a shaky foundation because once the algo is changed and your pages are filtered out, you are up for a complete rebuild.