On page recommendations focus on areas which can often be altered or amended using functions of the CMS. It's recommended that research be carried out as part of an SEO strategy prior to any significant changes.
Often (though not always) the title tag and meta-description are used as the link and excerpt within the snippet in Google's search result. They are also frequently used by social networks to automatically generate a snippet when a user shares your web page. It's important to make sure that your title tags and meta descriptions are not only optimised for search engines but your users as well.
When determining the relevancy of a page to a user's search query, Google and other search engines will take your sites title tags into account. While title tags are one of many ranking factors they are weighted heavily within Google's algorithm and vital for building authority to the page. It's therefore important to make sure that they are optimised to incorporate the terms that your website is targeting.
The page title shouldn't exceed 512 pixels worth of space, there are handy tools that calculate this for you online here.
Meta descriptions are often used within the search result snippet to give searchers a brief description of the page. Typically these shouldn't exceed 155 characters.
It can be an indicator of poor quality if every page on the website uses the same meta description therefore you should use a custom one for each page. Google will automatically select relevant text to display if there isn't a meta description present.
Google has expressed that the meta keywords tag no longer provides any value within organic listings for websites of this nature. That said, Bing has been known to use the meta keywords tag as a negative ranking factor; if a large amount of keywords are used in a spammy fashion it can be interpreted as spam.
The content of the page is one of the biggest factors within Google's (and many other search engine's) ranking algorithms. The search engine will use when determining how relevant a page is to a user's search query. You should aim to include the core keyword for the page within its content, however don't overuse it.
There is no scientific rule of thumb as to how many times a keyword should be used within a page. Referring back to Google's basic principles you should "Make pages primarily for users, not for search engines". With this in mind it's usually worth asking yourself whether the content would make sense if read aloud.
Generally you'll find that different sections of your website naturally target different keywords. Keep this in mind and make sure that what you're targeting is relevant to the content of the page.
There are instances when more than one URL can be used to access the same page, for example many sites can be accessed with or without the ‘www' in their URL (www.example.com vs example.com). This can be perceived as duplicate content therefore it's important to make sure that pages can only be accessed through one URL. To do this, a redirect should be used to send both the search engine and the user to the canonical (correct) version of the page.