Internet marketing, which includes SEO and SEM, requires formulating and implementing effective strategies to draw more targeted traffic that can eventually be converted into customers. Although every business must consider optimizing their websites in the search engines, for e-commerce website it is an 'absolute must'.

1. Know your Audience
2. Set a Goal
3. Select the right SEO techniques
4. Measure the Results
5. Make proper adjustments

Best Effective SEO techniques are:
On page Optimization Techniques:
Keyword Research
Title Tag
Meta Description
Sitemaps
URL Structure
Image Optimization
Update content regularly
Keyword Density
Headers Tag

Off page Optimization techniques are:
Micro Blogging
Forum posting
guest posting
Article Submission
Directory Submission
Local Listings
Infographics
Video Posting
Image backlinking
Social Bookmarking
Blog Commenting

I think you need to do both On-page and Off-page activities. It helps you optimize your website