Put simply, on-page optimisation means gearing your websites content to match the likely search activities of your target customers. The most important thing is content, specifically text.
Ecommerce websites traditionally fare well in search engine rankings because every product on an ecommerce website should include a large amount of textual content for the search engine robots to spider. For each product you have, include a decent amount of text in the product description - ideally 100 words, or more. In addition, use product names that include the type of product that you are selling. For instance, a pair of red trainers should be named "Red [brand name] Men's Trainers, White Laces, 3 Stripes", rather than simply "Red Trainers". The combination of words should match the likely search phrase that your potential customers use.
Following on the principle of putting such keywords in to your product names, you should continue this approach when naming product categories and even page names. A category named "[brand name] Men's Trainers" is better than "Men's", for instance.
You should pick a domain name that contains what you sell. For instance, "www.trainersandshoes.com" instead of "www.joebloggs.com".
The most important page on your website is your home page. A home page should include 300 words of descriptive text, broken down in to header titles (h1, h2, h3 etc...) and paragraphs. Sellr's text editors allow you to do this, and the header title tag and paragraph format is used extensively throughout the Sellr template structure. The home page text should be regularly tweaked, adapted and updated to include content that is relevant to your current marketing and business direction.It is your primary port of call for the search engine spiders, so it has to be relevant to what you're selling. For instance, it is counter-productive to have a home page of text optimised for selling summer clothes when you are trying to push winter ranges.
Additionally, search engines base the regularity of their visits to your webpages based on the frequency of changes to them. Regularly updating your home page (and other) text is a good way to ensure that the spiders visit your website frequently, index your new product pages and improve your rankings.
Your website name is very important. Your website name is included in the Title tag of your home page, among others. The home page Title tag is regarded as the most important tag on your entire website by the search engines. Whilst it can only be used to include a certain amount of text (a few words), you should use this to tell the search engines what it is you are selling. For instance, a website name of "Joe Blogg's Online Store" should be renamed to "Joe Blogg's Shoes, Trainers, Casual & Formal Men's & Women's Footwear".
Sellr auto-populates some of the traditional meta-tags (meta description and meta keywords). Neither are widely used by modern search engines for establishing rankings, and you shouldn't worry about these. We include this functionality purely for completeness. Visible text on your webpages is what the search engines are interested in.
Additional pages such as an "About Us" page, a "Delivery Information" page etc... are good ways of providing plenty of extra textual content for the search engines to read. Chances are your customers will ignore much of this content, however the search engines will index it.
Contact information is important. It establishes credibility, and search engines reward that. An address, email address and, most importantly, a land line phone number are very important. If you can't put your phone number on each page, ensure it is on your contact page and your home page.