There are many factors making up the search engine algorithms that decide where a website will be placed in its rankings. But what's the most important commodity to your website that you have 100% control over? The words and the content.
Whereas content has always been of the utmost importance, five or so years ago we were concerned largely with code and page tweaking, as well as off-site optimisation techniques such as link building. In this day and age of social media voting and various other networks that can be levered to drive traffic, the actual content has never been more important.
With regards to search engine optimisation, a lot is said regarding the importance of links, keywords and title tags. None of these should be ignored when building a website - keyword research should be carried out thoroughly, the title tags unique and optimised for each page, and link building pursued in whichever way you see best fit. But none of this should be carried out at the expense of the actual on-site content.
There's all manner of off-site trickery and quirks that can be employed to increase your natural search engine ranking and drive traffic to your website. If a visitor arrives and finds nothing of any relevant value to what they were searching for, or badly written copy littered with typos and grammatical errors, then they're not going to stick around. If your website is selling a service or product this is commercial suicide.
The end-users should always be considered the most important people when creating website content. After all, it's they, and they alone, that are the measure of a websites success. Whether this is through conversions, sales, sale leads, or simply traffic with a low bounce-rate it's this human being on the other end of the monitor that makes or breaks a website, not the search engine.
It's important to get your point across and remain coherent for each and every page, even the ones you're not actively trying to achieve rankings for. Remain consistent and treat each page as being of equal value.
Most importantly your homepage should be an overview of the rest of the website, stating its purpose and the message you're trying to get across. The copy should be lean and shaved of any excess baggage, so somebody who's arrived at your website will immediately know that this is the place that will best serve their needs.
Copywriters always stress the acronym 'WIIFM' as being the most important factor when writing sales copy. This means 'What's In It For Me?' and is what any potential customer or visitor to your website will be thinking when they arrive. Therefore, use the homepage to tell them. If you're providing information, let visitors know what they can expect to find and why your website is the place to find it over anybody else's. If you're selling products or services, ensure user are made fully aware of how they'll benefit from them.
Good, well written content that's engaging, informative and unique, not only benefits users but also you, the webmaster.
Obviously, if you're providing a useful resource for users, whether through a blog, regularly updated articles, or just the core pages of your website itself, then you'll inevitably develop a base of regularly returning readers. If you're actually selling something through your website then this increases the opportunities for successful conversions.
But as a side-effect of this, and perhaps most importantly with regards to SEO and improving your search engine rankings, there's all the naturally formed links your website will enjoy.
Links are still gold-dust when looking to rank highly in the search engines and the naturally formed link will always remain the bedrock that Google was built on. If you're providing decent, informative content on your web pages, then people will naturally link to it. This can be given a boost by promoting your website around various social networks - the traffic from these sites is notoriously unqualified and for the most part won't lead to a significant rise in conversions, but as a way of attracting links into your website, they're invaluable.
Remember: Getting users to your website spells victory on the battlefield, keeping them there is where the war is won.