Basically, there are several "parts" to getting better Rankings.

The importance of each part depends on the Search Engine... but all should possess some significance.

1) Keywords and Description.
Though considered "oud of date", and some search engines apparently don't use them, it doesn't hurt to include them, (as far as I know!).
They should be specific... you may want a few that appear through most of the site, but there should be "unique" or "targeted" keywords for each page, along with a distinct description that is informative.
So think of having 2 sets of Keywords and Descriptions; the first set are the Unique/specific one, the second set are the generic that appear throughout the site.
Try to include the Keywords into the Description.


2) Title Tag.
This is apparently more important to Google than the Keywords.
It is meant to be an indication of the page content.
I tend to make it hold the Site Name (Company Name), and the Page Title. Some people suggest attaching a few Keywords to it as well, (I disagree with this, but it may actually work!).
Making the Title match the Keywords / Description phrase would help.


3) Use Header Tags.
The inclusion of Header Tags, (H1 etc.), seems to helpa fair bit.
There should only be a single <H1>... I make this consist of the Site Name... though you may want to include the Site Name and Page Title for a little extra "bang".
I use the <h2> tags to segregate the site for Accessibility (Header, Main Nav, Main Content, Footer etc.).
I then apply <h3> to indicate Cotnent, such as the "page Title" displayed on a page is wrapped within <h3>.


4) Strong Content
This is probably the Most important bit; what your page/s deal with.
If you don't have any real textual content, you are not going to do well.
Additionally, having a huge amount of content on a page with little/few uses of the Keywords / Descriptive Phrases will not help either.
The ratios vary, as does the location... there have been times when having Keywords near the top of the Documet had more weight than those at the bottom.
So go for even dispersement.
If you think a typical paragraph is 3 to 5 Sentences, make sure you have at least 1 Keyword in the first and last sentence.
Also try to maintain a minimum of 2 Paragraphs, and if possible avoid huge documents, (if needed, split them over a couple of a pages).
A technique I use is to always have an "introduction" section at the top of the Document, (after the Page Title).
This section normally has a couple of the Keywords in it, and almost matches one of the Description Phrases.


5) Links to your site.
For search engines like google, this seems very important.
The more "quality" links to your site, the higher you will score.
The problem is, for business sites, this is severely difficult, as the main sites that possess similar content are your competitors (well thought out google!).
Directories and Press Release Sites are okay, but some are not to be trusted (they are labled as spam-lists), and may cause more harm than good.
So do links from poor quality sites,
(thus bad sites linking to you can damage your scores... and you cannot stop them linking!).


6) Internal Information
This is sometimes overlooked, but some search engines apparently take note of Alt attribute for Image Tags and Title attribute for Link Tags.
Do not "keyword stuff", as google will penalise you.
Having a keyword in an Images Alt attribute with several other words is ok.
It is also good practice for the Title attibute in Links to be informative, and somewhat similar to the linked to pages Description.


7) Sitemaps
Another consideration is SiteMaps.
This not only provides additional Usability/Accessibility access, it provides search engine bots the ability to quickly see all the liks on the site.
You can have 2 types; Visitor Sitemap and XML Sitemap.
Visitors Sitemaps are thoose that people can use, (nicely formatted list of links etc.).
XML are things like the google sitemap 9.0.


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So, the end result should be that you have...

<Title>
<Keywords 1/2>
<Description 1/2>
<h1>
<h2>
<a>
<h3>
<p>
<img>
<a>

.... becomes ....

<html - xhtml>
<head>

<title>
Site Name + Page Title (+ Keywords1 ?)
</title>

<meta-keywords
Keywords 1/2 (Unique/Generic)
/>

<meta-description
Description 1/2 (Unique/Generic)
/>

</head>


<body>

<h1>
Site Name + Page Title (+ Keywords1 ?)
</h1>

<h2>
Header / Nav / Content / Footer etc.
</h2>

<a>
Link to Page Title + Partial Description for
Title attribute
</a>

<h3>
Page Title
</h3>

<p>
Paragraph 1 = Intro... 2 to 4 Keywords from
Keywords1, plus match parts of Description1.
</p>

<p>
Paragraph 2+ = Main Cotnent...
1 to 3 Keywords from Keywords1,
1 to 2 Keywords from Keywords2,
+ try to get a part of Description1,
+ try to get a part of Description2,
(this does not mean get all of the above into
a single Paragraph! Even it out over 4 to 8
Paragraphs)
</p>

<img>
Descriptive ALT attribute if the Image is
Content, with a single Keyword if at all
applicable!
(do not use ALT if simply for "prettiness")
</img>

<a>
In page links are always a good idea,
(to things like the Contact Us page!).
They may not score any points, but are
helpfull!
</a>

</body>

</html - /xhtml>


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So there you have it... that should be enough to get you going more than well enough.

As suggested previously, you may want to hire someone to write search engine optimised copy for you pages.
It is not cheap, but go for a company with a very well proven track record!
There are far to many "SEO Consultants" out there that do nothing more than use stupid software and automatted submit scripts - get the real deal, they are worth the money.


Please Note:
I am not an SEO consultant, nor claim to be highly knowledgable in regards to this... it is simply the steps I use, and most of the sites I have built do well enough following such a strategy (though suggestions on improvements always welcome ).