This post doesn't attempt to cover more obscure aspects of search engine optimization (SEO), but covers the basics that are really easy to overlook when you work on your site. Also, since Google is the major search player, I just refer to "Google" rather than trying to be more generic.
Step 0: Has Google indexed your site at all?
Go to google.com and do a search on site:your-site-name-here, like "site:http://bhphotovideo.com" to see if byphotovideo.com is indexed by Google. If there are no results, you're not indexed. Some ideas to get indexed: a) put in links from sites / pages you already have (for example, your profile on linkedin.com), b) get other sites to link to you (for example, you can comment on other peoples' blogs linking to your site), c) for blogs, use Pingomatic to automatically update other services of your site, and d) submit your site to Google for indexing (not sure that actually does anything though?).
Step 1: What are you trying to accomplish?
This one sounds so obvious and silly, but it's very easy to overlook. It's useful to just write down the search phrases you'd like to find your site. Of course the more specific the better, since generic terms will be very difficult to get high rankings on. For example, I knew I wanted people to find this site if they typed my name and a little about me (for example, "David Hobbs CMS").
Step 2: Make sure your keywords are in the title and header tags, as well as in the text users will see (and preferably in the domain and URL)
You may not have control over the domain and URL (if you are in some content management systems), but you should at least make sure to have the title, header, and main text contain your terms.
Step 3: Track your progress.
Type your search terms into Google and see how high in the rankings you appear. If you have already gotten good results (first page of results?), it may be time to set your goals higher. For instance, for this site I'm now interested in shooting for more topic-based search phrases such as "multilingual CMS" (currently the 14th page of results). Also, you will want to look for dips in the performance of your search phrases. This is especially relevant to test before and after any changes you make to your site/system. If you're working with a client on their site, by having the metrics (and search goals) before you start you'll be able to more objectively discuss the search performance of their site. Another angle is to look at the terms that people are using to actually find your site. You may find interest in your site from unexpected angles that you may wish to further enhance (for instance, people are finding my site with phrases such as "annotate excel graph", so I may put a more generic introduction to that blog entry).
Repeat.
The first step, to get into the Google index at all, involved getting links to your site. As you proceed, of course you also want to have higher and higher quality sites link to you. As mentioned in the previous step, your search goals will also probably change, and you'll want to add/reword/reconfigure portions of your site (per Step 2 above) to optimize for those new goals.
