SEO (Search Engine Optimisation) is a very hard technique to master and no one ever does entirely, partly because it is so vast and much of it based on ideas and assumptions. Also the rules and regulations of Search Engine Optimisation, also known as the algorithm is constantly changing so you need to be on the ball all the time looking out for the latest updates and changes.
Unfortunately there are still some, what are classed as, “Bad” or “Black hat” SEO techniques floating around that the not so savvy marketeer may be tempted to use. These techniques can not only have little or no effect on the actually rankings of a site but can even have a very detrimental effect on the rankings leaving a site devalued in the search results or even omitted entirely. If this happens, it can be very hard to recover from it and often it can take months and months to get a to be indexed again.
When it comes to SEO it is best to leave it to the experts, and when I say experts I mean the people who actually get results not just advertise and an expert.