Top 5 SEO Problems found in many Web sites

1. Not Enough Content

Most ecommerce sites tend to be great with putting content on their product pages, but forget about their homepage and their category pages. Content rich product pages are great when people are searching for your products, but what about people with slightly broader searches? If your category pages just have a list of products on them but no content about the category, then you are missing a big opportunity.

2. Bad URLs

URLs serve a few purposes in SEO. Firstly, Google uses keywords in the URLs as ranking factor. Not only will that lack a keyword boost for Google, but it’s not a great search result, it doesn’t entice people to click.

3. Good Met descriptions

Meta description tags aren’t used by Google as a ranking factor, so tweaking them won’t make you rank any higher.
However, the meta description tag is often used by Google to show the abstract that appears in the search results. As a result, a well written meta description tag is more likely to entice people to click on your listing rather than your competitors listing.
4. No Alt Tags

Google and other major search engines weigh the text in alt tags at least as high as headings, so it’s definitely worth your trouble. Ideally your alt text will be custom written for every image,
5. Canonicalization Issues

Canonicalization is when one page has multiple URLs.

The canonical tag can be a good way to solve these problems.
// <link rel="canonical" href="http://www.site.com/page"/>
I recommend you to read Top 5 Bad SEO Ideas and Importance of Title Tag in SEO