There are many, many things that influence Google search rankings. Google have stated that their search algorithms 'rely on more than 200 unique signals' – some of which you'd expect, some you wouldn't. Nobody (outside of Google) knows what they are exactly, but through practice, testing and collaboration we can work out the best practices.
Of course, a lot of what goes into search engine optimisation is technical and beyond what the ordinary layman needs to know (if they're using a digital marketing agency to do the leg work for them), but the end goal is to create a website experience that's user-friendly, authoritative and likely to be shared.
Along the way to the SEO holy-grail, it's important to avoid these common SEO pitfalls:
Not Keeping Up To Date
Old practices are BAD! Stuffing keywords into the page, overdoing internal links, relying on a high quantity of external links (rather than quality), buying external backlinks, spinning articles through syndication sites, using automated link building software to spam blogs and directories – all of these techniques are dated or black hat. If it's the sort of stuff you're still doing then you're out of date and risking not only a drop in rankings but banishment from Google altogether.
We saw a post on a webmaster forum where a person was wondering why their site had dropped down the rankings – he/she had bought a keyword specific domain, keyword stuffed page URL and about a 90% keyword density, not to mention a ridiculous blatant 'overly optimised' site navigation/internal linking structure. It was a site designed just for the search engines and nothing more. It was terrible to look at, read like spam and had very little user value. No surprise that after the recent Google Penguin and Panda updates their site dropped from the rankings.
Trying To Rush Your SEO
Search engine optimisation is a long-term process that cannot be rushed. Many historical factors can have an influence on the ranking of a website including domain age (i.e. how old the website is), number of links pointing to your site (this will naturally grow over time) and other factors. Trying to rush search engine rankings is a dangerous game indeed.
Taking shortcuts will see you lose out in the long run. Black hat techniques are dangerous for this reason and should be avoided. Something as simple as buying links can lead to your site being banned altogether from the rankings. There is no quick fix answer when it comes to SEO, so if you need short term results it's better to focus your initial efforts on Pay Per Click advertising and work on SEO over time.
There are of course exceptions – for example if your product/service is so magnificently mind-blowing that it goes viral as soon as it launches and the whole internet/media/world is talking about it then that's bound to send your site skyrocketing to the top or if your company is in such a unique niche that there's minimal competition, that will make life easier too!
SEO is important, but neglecting PPC will leave you missing out on a lucrative potential revenue stream. It is also akin to throwing all your search eggs in one basket. If you rely exclusively on SEO your business could suffer greatly through no fault of your own simply through Google algorithm updates and changes.
Concentrating on One Area
SEO is influenced by many things. Internal, external, social, local, it's important not to neglect one area in favour on another. You could spend all your time working on raising the external profile of your site through link building and social networking, but if you neglect the technical aspects of the site you'll soon find you're losing visitors before they even get started thanks to your slow loading, broken and awkward website. On the other side of the coin, you could have the fastest, most user-friendly website in the world, but without any marketing and external SEO, how will you attract the visitors and potential customers?
Forgetting The User
The main aim for Google is to return the best possible results for the user, so that should be your aim as well. Build an easy-to-use website, full of useful content and excellent products, with logical e-commerce systems (where appropriate) and you'll keep the user on the page when they arrive. With luck (and good pricing) you'll turn them into a sale and a return customer. It's common sense.
Build a site just for the sake of SEO and high rankings and you'll just find a website that people visit but never buy from with a high bounce rate as visitors arrive and instantly leave. Remember the user!