Tags

HTML titles have always been and remain the most important HTML signal that search engines use to understand what a page is about.
Craft unique, descriptive titles for each of your pages.
Each page’s <Title> tag must be unique
Put inside the <HEAD> area
Think Keywords
Don’t start with your company name
Consider Prominence- Important keywords near the front
Use Title Case (The first letter of every word should be capitalized)
Don’t write a sentence
40-60 characters including spaces

Example:

The Title Tag immediately tells users what they can find on the page. Assuming that the searcher is looking for ferries and mini cruises.

2. Header tags

Header tags are a formal way to identify key selections of a web page.
Search engines use them as clues to what a page is about.
If the words you want to be found for are in the header tag, you have a slightly increased chance of appearing in searches for those words
Header tags are supposed to make content as easy to read for users as it is for the search engines.
Useful when they reflect logical structure or (outline)

Examples:

3. Description Tags

Don’t make it too long ( Limit to under 200 characters)
Use keywords in the tag text
Use Title Case (The first letter of every word should be capitalized)
Think of this as a sales pitch, you are trying to encourage people to click that page.
Should be written as snippets of information.
Probably not used for ranking purposes by Google, but used by some other search engines.

Still important!

4. Google Meta Tags( support.google.com/webmasters/answer/79812)