There is little value to having a website if nobody can find it. The way that most people will find your site is through the search engines. In order for that to happen your site must be properly optimized.
The first thing that you need to keep in mind about search engine optimization is that it is a continuous process. This is something that many webmasters fail to understand. They seem to think that if they can get their site to rank in the number one spot for the keyword they are targeting they are done. This is not the case, if you stop adding links to your site you will find that you quickly get overtaken by the sites behind you. Not only that but just because you rank first for one keyword doesn't mean that you can't rank first for other keywords. You need to keep doing search engine optimization for as long as you have your site.
The process of optimizing your site for search engines is not all that hard, but it is time consuming and tedious. This is why most people out source it. There are basically two parts to search engine optimization; the first of these is called on page optimization. The goal here is simply to make it clear to the search engines what your site is about. You do this by making sure that your page is laid out in the way that the search engines expect it to be.
The on page optimization is the easy part. The far more challenging part when is off page optimization. This basically consists of getting links to your site. The search engines need a way to determine which site is the best one for each search term. Unfortunately there algorithm can't make a judgment like that so they need another way to do it. The way they have come up with is to use the number of incoming links on the logic that the site with the most links must be the best. There are other factors at play as some links are more valuable than others but in large part it comes down to getting as many links to your site as possible.
Since getting links to your site is such a time consuming job most people will outsource it, but you do need to be careful here. Search engine optimization is actually frowned on by the search engines; they view it as gaming the system. They know that all webmasters do it and there are certain things that they are willing to accept, some they even want you to do. However there are a lot of things that can get your site removed from the search results altogether. You need to make sure that if you outsource the job you hire somebody who won't get you delisted.