Quick search ranking improvements can be had by optimizing the existing website. On-page optimization is concerned with meta tags, content, images and other factors, all relating to the website and its contents.
Should be 'Search Engine Friendly'
URL's should not be filled with punctuation, but rather should be easy to read, remember, logical, short sweet and logical. Wordpress sites do this via permalinks. eCommerce and CMS's often have search engine friendly plugins.
Meta Titles - Length
Max length of 64 characters
The least common denominator approach amongst Google, Bing, Ask, Yahoo means that titles should be limited to 64 characters. Anything longer and sites risk getting odd results, as search engines truncate or replace the title with other terms.
Meta Titles - Originality
Title should be unique
Each and every page needs a unique title, named appropriately to the page content. Company names should go at the end, if at all, and be separated with symbols such as: ~ | or -
Meta Descriptions - Length
Max length of 140 characters
The least common denominator amongst popular search engines limits meta descriptions to a maximum length of 140 characters. Anything more will be truncated, or replaced by some engines.
Meta Descriptions - Call to Action
Give people a reason to click
Meta descriptions are what people see in the search results. As such, it's just like any other advertisement - competing against those around it. So, in order to get a maximum click through rate, it should give people a good reason to visit the site and set the expectation for what they will find after clicking.
Headers (H1/H2/H3) Tags - Keywords
Header Keywords Use - Avoid Over-Use
Gone are the days where mainstream SEO experts would recommend stuffing keywords into header tags. It's now advised to make them look natural, read human friendly, introduce or summarize the main point and OCCASIONALLY mention a keyword which is being optimized.
Keywords in Content - Recency and Primacy
Mention early and mention late
Web pages, like speeches, start with someone telling you what they're going to say, saying it, then telling you what they said. So too do search engines then expect keywords describing the page to appear at the top (primacy) and at the bottom (recency) of the page.
Images - Keywords in Alt Tags
Avoid too much of a good thing
Images have alt tags so that people who are visually impaired, or who have images disabled, will be able to know what's happening on a web page. Alt tags are not a good home for massive keyword stuffing. Use natural terms that fit the image and occasionally sprinkle in a keyword here or there.
Keywords in Content - Bold or Italics
Emphasis can make a strong point
Keywords can be emphasized in content by the use of bold, italics or both. This signals people, and search engines, that you're making an important point. Too much of this and the text becomes very confusing to read and bad for the user.