There are three main Meta tags that should be in all websites. They are listed below by importance. 

Title:

What Is The TITLE Element?

Towards the top of a webpage's HTML code, within the <head></head> tags, is the <title> element. This element is used to show the title of the page in the "title bar" of a web browser. The <title> element serves the purpose of being your headline or "one line sting" for a given page. This element is perhaps the single most important component when it comes to search engine rankings, as its contents are almost always the title that search engines use to list your website in their results pages (SERPS).

Correctly Using the TITLE Element

For maximum effect, the <title> should be no longer than 60 characters (including spaces) and have correct grammar. Be sure not to abuse this element by "stuffing" it with keywords. This increases the chance of search engines banning your webpage and simultaneously decreasing the likelihood of catching the visitor's attention—neither of which are a good thing!

In search engine terms, the <title> element is said to carry significant weight, meaning that words appearing in this element have a significant importance. Given that this element carries so much weight, it should accurately describe the contents of the webpage while still containing your target keywords.

To ensure that this element does not get buried by HTML & JavaScript code, it should be located at the very beginning of the <head> element.

The title is probably the most important part of your site to evaluate, as it is the most frequently searched component by search engines, and should state exactly what your site is about, without use of any superlatives. To get high rankings, the title must include your most important keywords. Example of a Title: "Dave's Interior Designs - Decorating the Inside of England's Homes".

Given that search engines place a great degree of emphasis on the <title></title> tag, many people assume that using more than one tag will increase their ranking. This is not true, even though many spammers continue to use multiple <title></title> tags.

A well-constructed page should contain ONLY one <title></title> tag, which should be the very first tag inside the <head></head> tag.

Search engines can easily detect the use of multiple <title></title> tags and have been known to ban Websites that employ such spamming methods!

Here is an example of an optimized Title tag and where it is found in an HTML file:

<html>
<head>
<title>Search Engine Submission & Optimization Services </title>
<meta name="description" content="Providing professional search engine submission and promotion services. Let us increase your traffic level.">
<meta name="keywords" content="search, engine, submission, optimize, optimise, promote">

Meta Description:

The "meta description" tag is located at the top of your page within the <HEAD> </HEAD> tags. 

This tag gives you the opportunity to put forward a brief description of the contents of the webpage. The recommended length for this tag is 128 characters maximum (including spaces) for cross-engine compliance, although you may wish to extend its length to a 200 character maximum, which is permissible so long as the tag is not "stuffed" with keywords and the description is an accurate reflection of the contents of the webpage.

This tag can be seen on the SERPS (Search Engine Results Pages) and if worded correctly may significantly increase the quantity of traffic driven to your website.

Here is an example of an optimized Meta description tag and where it is found in an HTML file:

<html>
<head>
<title>Search Engine Submission & Optimization Services </title>
<meta name="description" content="Providing professional search engine submission and promotion services. Let us increase your traffic level.">
<meta name="keywords" content="search, engine, submission, optimize, optimise, promote">

Your website description should be around 20 words summary of the content of your site. This description should contain some of the keywords and be sure to avoid marketing language. Example of Description: "A full service provider of interior design services - decorating, painting, furniture, and color schemes for your house".

Meta Keywords:

What Is The Meta Keywords Tag?

The Meta Tag Keywords should be those words or phrases that you think people will use when trying to look for a site like yours on search engines. Incorporating keywords in your site's body text - To rank high on search results your website must have a focus and the text should emphasize it. Incorporate many keywords within your site's first paragraphs (50 words) and repeat them throughout the text. The right keywords for your website should be specific enough to describe your website's interest, yet general enough for potential customers to use as search phrase in the search engines.

The Meta keywords tag is located at the top of your page within the head tag. This tag has been around for years and at one point was a very important component of search engine optimization. While this tag is now ignored by virtually all fully automatic spiders, it may still carry a small degree of weight in older search engines. The reason for which this tag carries virtually no weight is obvious. This tag is visible only to robots/spiders and is not seen by human visitors, so it can be easily abused.

Because older search engines may still support this tag, it is wise to include it on your Webpages. However, it should be short, spam-free, and clean. The tag should contain words that accurately describe the content of the Webpage, be no longer than 250 characters (including spaces) in length, should contain no repeated keywords, and each word should be comma delimited. Abuse of this tag is very easily detectable, and search engines will ban your Website if you stuff keywords or use keywords that are unrelated to the Webpage.

Where Does This Tag Go?

The optimal location of this tag is within the head tag, directly below the Meta description tag. The string of keywords should begin with your most targeted. Be wise and ensure that you include alternate keywords and alternate spellings that may be used frequently by your potential audience. For instance, in Europe the correct spelling for "optimize" is "optimise".

Here is an example of an optimized meta keywords tag:

<html>
<head>
<title>Search Engine Submission & Optimization Services</title>
<meta name="description" content="Page Description" />
<meta name="keywords" content="search, engine, submission, optimize, optimise" />
<link rel="stylesheet" href="/your/stylesheet.css" type="text/css" />
<script type="text/javascript" src="/your/javascript.js"> </script>