This article contains almost everything you need to know about SEO, although even Google do not know everything about how it works.
If you are serious about getting to the top of the first page of a Google search, you have to know a lot about SEO. Once you know a good deal about search engine optimization, you can choose to focus on the algorithms as strictly as possible, or you can just write with the understanding in the back of your mind.
Title choice is the most important thing to consider, because when you name your article, or home page something that won't have any chance of being found in a Google search, you doom it right then.
Title is the first, and most important Google algorithm. Google looks at the title before anything else, and you have to pick a title that will get typed into Google by many people, and also, a title that does not have too much competition.
For example, I titled this article: What do you need to know about SEO? If I had titled it SEO, I never would have been able to compete with all the SEO companies out there, and if I had titled it: SEO Makes Learning Fun, there would be a ridiculously small amount of people who would type that exact phrase into a Google search.
Keywords are very important to give Google the impression that your article is relevant to the search, but while you do have to include a reasonable amount of keywords in the article, (in my case SEO, what do you need to know about SEO, etc), it is just as important to include a lot of complimentary keywords, and keyword phrases, that Google recognizes are related to the subject matter in the title.
For example, the complimentary keywords that are related to SEO, are search engine optimization, keywords, title, back links, traffic, link text, link weight, and many other words like those.
You can use Google's keyword tool to get a list of the words it thinks are the most relevant to the title of your article, or site, and then you try to include the most relevant most often, and make sure you include all of them at least once. I generally don't use the keyword tool, I just guess the relevant words.
There are two schools of thought on adding photos into your pages. On the one hand, Google likes to see photos, but on the other, it doesn't like a page that takes too long to load.
If you add the photos, and your page takes more than a few seconds to load, then imagine how long it will take on the other side of the world. You have to decide if it is worth it to add the photos at all, I suggest maybe just one small one, if it it doesn't affect the loading time too much.
Subheadings are a good way to break up the text in your article into relevant categories, and it is a fairly big part of on-page optimization. A page with subheadings looks more proffessional, and the keywords in the subheadings give Google a better idea of what your page is about.
Use bold, large print subheadings, that include your keywords, and complimentary keywords, but don't go overboard with the amount of bold, large text you use.
Google tends to like to see relevant links coming out of your page to other sites, and it is probably better if you don't make too many to the same domain, or to sites you created, but send a relevant link to other people's stuff, just to show you aren't biased.
You don't want to divide the link weight that flows from your page too much, (provided you have do follow links), and it depends what you are trying to do, whether you want to advertise many sites, or just pass as much link weight as possible to one in particular.
In this case, I wanted to send a couple of links from this article, to a couple of different articles I wrote on different domains about SEO, so I choose some relevant link text, (good to have many different links from different related link text), and that's it.
Back links are links from other sites leading to the original page. You can make back links from hundreds of different sites, like relevant articles, social bookmarking sites, social networkings sites, etc. You can submit to search engines, (although they will probably index you anyway), and post comments with your link in a signature on a relevant forum, or blog.
The thing to be aware of, is some sites have no follow links, so you need an SEO tool to check whether a site is giving you a do follow link, (which does let link weight flow), or not. You can get a good free browser add-on for firefox from SEO Book, which among other things, allows you to check for no follow links. Also, download another free browser add-on, Add This. You can google that one.