On-page SEO is about optimizing your website content using techniques that include unique page titles, META descriptions, heading tags, highlight tags, alt and title attributes, and last but not the least, content optimisation. Here's what each of these terms really mean.

Unique Page Titles - The Title Tag

Title tags are not only displayed in your browser but are also used by the search engines as the title of your listing in the SERPs. Don't rush into using just any old title. Think about the most appropriate title for the particular page and use it. Google, Yahoo and MSN all look favourably on unique title tags.

Things you should keep in mind when composing your title tags:
-Every page of your site should have its own unique title
-Don't use a single title tag for the entire site
-Keep the title between 10-12 words in length
-Think of the title tag as a short ad copy that as user sees on the SERPs.

META descriptions

META tags are currently not as relevant as they once were. This is because META tags became plagued by webmasters trying to spam the search engines. That being said, you can still use META tags as part of your on-page SEO. Here are a few you should use:

The description tag is a very important META tag. Again, it's displayed in the SERPs and should be composed with careful consideration. A description tag assigns an individual identity to each page and well written, can positively influence users into visiting your website. Use only the most relevant keywords in your description tag and try to keep the word count to around 25-30 words max.

The NOODP Tag is a relatively new tag and guides the search engines to not display the title and description tags used for your website listing at DMOZ.

Heading Tags

A great headline is a perfect hit with both, the reader and the search engines. Using Header tags will tell the search engine which "words" are important in the context of your page and as such are given more weight by search engines than regular body copy.

Highlight Tags

When adding your keywords to a web page, it is helpful from an SEO perspective to highlight some of them with bold, italics, or emphasis tags to convey to the search engines that these keywords are important. Such tags are also given more weight than regular body copy.

ALT & Title Attributes

Use these two on-page SEO factors to describe both images and text links on your site. These help not just with search but also enhance the accessibility of your website for visually impaired users. Search engines use the alt tag in the same way they use the body text to rank your web page.

Content Optimization

This is a tough balancing act. Not only do you have to focus on your user and their ease of reading, but you also need to make sure that the content is search engine friendly. While users can get the gist of the content by its title, the search engines require a more comprehensive display of keywords and related terms throughout the page.

Strike the right chord by staying focused on the requirements of your users/prospective customers. Next weave the relevant keywords into the text to attract the search engines. A 2-8% keyword density is recommended.

Finally, keep the website content fresh and interesting so that the search engines always have something new to find and they will spider your site more frequently.