The first thing that you should know about search engine optimisation is that there are actually 2 different things to consider, these are your on-site optimisation, and then your off-site optimisation.
On-site optimisation refers to the important things on your website itself, like the structure of the site, the meta title, meta description, headings (H1, H2, etc), the content, and the interlinking and menus within the site.
The off-site optimisation refers to things like links that point at your site, since Google counts each of these as a vote for your website. Links have a different value depending on the quality of the site that they come from.
Your starting point should be to plan out your site and it’s structure before you get anywhere near to beginning to build it, and your aim should be to make it all fit logically together so that the structure is clear, it’s easy to find the things that you want, and it gives the visitor a good user experience because of this.
The generally accepted rule is that every page should be accessible within 3 clicks from any other page.
Probably the best way to do this is to break down the content that you plan on having on your website into chunks or sections, think about the logical steps that people would need or want to work through when they arrive at your site, and build it accoringly.
You menu system wants to be constructed with this in mind, and you might want to have a menu at the bottom of your website so that when people have reached the bottom of a page, they don’t need to scroll right back up to the top in order to go somewhere else.
It’s also a good idea to have links from within the content on the pages that lead to other relevant pages, to make it as easy as possible for your visitors to find more stuff that they are interested in – like I’ve done on this site.
If you’re using WordPress then there is a great plugin that will do this automatically for you, just use it sensibly.
Carefully creating your site structure and internal linking like this gives you the distinct advantage that not only do people find it easier to navigate around your website and find what they want, but also search engines can find their way around your site and work out how everything fits together.