You already have or you are thinking about developing a new website or a blog; let's be clear : your site,  regardless of its interest and its quality is useless if it is not visited by users ! Its visibility on Google and all search engines is absolutely fundamental.
We can summarize the objectives of SEO under  these three points:
-Make your site Visible ! (without visibility a site or blog does not exist).
-Attract a maximum of qualified traffic from search engines.
-Build a strong brand image for your website or blog.

Another very important element is regularly forgotten: stand out from the competition because if a lot of quality sites are equally visible, your will be drowned in the midst of a multitude of sites.
On this point Plusvisites is your best partner to help your site, not only to be visible but to emerge from competition.

What does search engine optimization mean?

Search engine optimization is the process that enables search engines to better identify, index, and rank your website. The primary reason for optimizing a website is to improve rankings on search engine results pages.

The SEO (Search Engine Optimisation) refers to all the techniques involved in the ranking of a website on search engines.
A Search Engine is an online internet service allowing users to find information quickly with one or more keywords placed in a search form. The major search engines are Google of course, the world leader but also Bing, a Microsoft affiliate, Yahoo or Baidu. 
A search engine works through servers called robots or crawlers that are loaded to browse the web, following the Web million links pages of millions of websites to index their content in huge databases that will be solicited during a user search. No search engine can browse all the pages in a day (this process typically takes several weeks), each engine adopts its own strategy and attempts to determine the frequency of the sites updates. Then it returns a list of results (SERP for Search Engine Result Pages) that contains links to pages with either the beginning of the text of the page or the text specified by the creator of the page with the specific tags called meta -tags, or extract the page containing the search terms.
The different responses to a specific request are then ranked in order of relevance, corresponding to specific criteria search engine, such as the percentage of words that match the search, the number of links pointing to each page, their density index ... and the pages are first selected according to their relevance to the search, and then positioned in a specific order determined by the engine's algorithm according to criteria such as positioning the confidence index (TrustRank), PageRank, the clicks in the results, the time spent, bounce rate, links ...
This is the most secret part of SEO, the algorithm is a complex mathematical formula that can be defined as follows: An algorithm is complex system of indexing the pages of the search engines that meets the criteria well individuals, combining the content and form of content on the Internet.
Indeed, with the evolution and the exponential development of websites and blogs, it has become a priority for developers to build sophisticated algorithms that best meet the needs of Internet users. There are many criteria taken into account by the algorithms of search engines, such as the age of the domain name, the bounce rate, an active presence on social networks ...

Search engines follow a set of rules, known as an algorithm. Exactly how a particular search engine's algorithm works is a closely kept trade secret. However, all major search engines follow the general rules (frequency of a keyword in a web page, meta tags, the number of links that point to your site, content, etc...)
We detail below most of these general rules that we recommend for your website:

The contents
For a given search engines look for the most relevant results and more complete. It is therefore essential to focus on creating a quality and original content. Social networks are an excellent vehicle to promote content and to identify the interests that readers relate to your site. Another very important element: to update. The fact to update pages of the site means that the site is present, alive and not frozen.
Google Panda: Google Panda is a filter that prevents low quality sites and/or pages from ranking well in the search engine results page. 

Optimizing "Title" and "Meta Description" for each page of your site 

SEO is directly linked to key words:these keywords are used by visitors during their search.
Il is fundamental to determine precisely which keywords are critical for your werbsite. The keywords that you think are not always match the keywords used by visitors, they tend to use the shortest possible terms even with misspellings.
Foolllowing tools will help you to compare the search volumes of a keyword compared to another,  and give suggestions:

Google trends
Google adwords keywords planner
Sistrix.com
Wordtracker.com

This last tool wil help you to know the key words used by competition:
Semrush.com

On top of all SEO rules described previously we list below specific tips for e-commerce sites: 

-Do Not use the product descriptions provided by manufacturers, but provide a product description which is optimized for SEO

-Optimize images

-Use unique meta description for each page

-Add an evaluation field by your customers for each product

-Add links to your products on your home page

-Get your customers advises 

-Follow your traffic conversions 

Google Analytics is a great tool to analyze your traffic and identify your areas for improvement.

If you have just created a new website, it is rather advisable to start by setting up a good adverting campaign (SEA for Search Engine Advertising) , it will help you to boost your visibility on the search engines.  

What is Search Engine Advertising ? 

Search engine advertising (SEA) is a branch of online marketing. In SEA, advertisements in the form of a text or images are posted on search engines such as Google , Bings ...The advertisements are then placed prominently in the search engine result page.
The purchase of quality traffic is an excellent complement to improve your site ranking on the search engines atv a reasonable cost.