SEO techniques can be classified into two broad categories: techniques that search engine companies recommend as part of good design ("white hat"), and those techniques of which search engines do not approve ("black hat"). The search engines attempt to minimize the effect of the latter, among them spamdexing. Industry commentators have classified these methods, and the practitioners who employ them, as either white hat SEO, or black hat SEO.[50] White hats tend to produce results that last a long time, whereas black hats anticipate that their sites may eventually be banned either temporarily or permanently once the search engines discover what they are doing.[51]
Sometimes, Google turns up the dial on demands on ‘quality’, and if your site falls short, a website traffic crunch is assured. Some sites invite problems ignoring Google’s ‘rules’ and some sites inadvertently introduce technical problems to their site after the date of a major algorithm update and are then impacted negatively by later refreshes of the algorithm.
Conventionally, we think linearly about content and keywords; we build a website, and then launch search engine marketing campaigns to drive users to our content.  That approach has its limits. When we think about strategy at Wpromote, we think about  a circular process; since our keyword research reflects both what users are seeking and the way that the search engines (particularly Google) "think" about keywords, we let that help to drive our content strategy.
That content CAN be on links to your own content on other pages, but if you are really helping a user understand a topic – you should be LINKING OUT to other helpful resources e.g. other websites.A website that does not link out to ANY other website could be interpreted accurately to be at least, self-serving. I can’t think of a website that is the true end-point of the web.

It is important you spread all that real ‘PageRank’ – or link equity – to your sales keyword / phrase rich sales pages, and as much remains to the rest of the site pages, so Google does not ‘demote’ pages into oblivion –  or ‘supplemental results’ as we old timers knew them back in the day. Again – this is slightly old school – but it gets me by, even today.
It's important to check that you have a mix of head terms and long-tail terms because it'll give you a keyword strategy that's well balanced with long-term goals and short-term wins. That's because head terms are generally searched more frequently, making them often (not always, but often) much more competitive and harder to rank for than long-tail terms. Think about it: Without even looking up search volume or difficulty, which of the following terms do you think would be harder to rank for?

Many think that Google won’t allow new websites to rank well for competitive terms until the web address “ages” and acquires “trust” in Google – I think this depends on the quality of the incoming links. Sometimes your site will rank high for a while then disappears for months. A “honeymoon period” to give you a taste of Google traffic, perhaps, or a period to better gauge your website quality from an actual user perspective.

Length of site domain registration; (I don’t see much benefit ON IT”S OWN even knowing “Valuable (legitimate) domains are often paid for several years in advance, while doorway (illegitimate) domains rarely are used for more than a year.”) – paying for a domain in advance just tells others you don’t want anyone else using this domain name, it is not much of an indication that you’re going to do something Google cares about).
Keywords are important because they are the linchpin between what people are searching for and the content you are providing to fill that need. Your goal in ranking on search engines is to drive organic traffic to your site from the search engine result pages (SERPs), and the keywords you choose to target (meaning, among other things, the ones you choose to include in your content) will determine what kind of traffic you get. If you own a golf shop, for example, you might want to rank for "new clubs" — but if you're not careful, you might end up attracting traffic that's interested in finding a new place to dance after dark.