As with many other things which are unseen, there is a lot of unnecessary mystery surrounding the use of meta-tags on web pages. The meta tags are information slots in the "head" portion of a web page.
Though there are several possible meta tags that may be included in the head of a web page, the ones which are most important for search engine optimization are the Title Tag, the Description tag and the Keywords tag.

TITLE TAG

The title tag is really one of the most important single things you can work on for improving your website's search engine results. Go to Google and make a search for any particular keyword. If you look at the top ten entries in that search you will see that all of them have this key word in the title, sometimes more than once. So when writing your title tag, it is helpful to have your keywords included in the title tag, and not only in the tag, near the beginning of the title.

Suppose that your company is the Acme Manufacturing Company and you are selling electric widgets and you are located in California. What should your title tag be? Most people would opt for the name of their company as the first word of the title. It makes sense, in that it looks good in the blue strip at the top of the browser, but it doesn't necessarily help you to get a good ranking in search results for your keywords "electric widgets, California".

The first few words of your title tag are very important. People may not be searching for Acme Manufacturing, unless it is a very important brand, but they are searching for electric widgets, and they may not want to purchase it from someone in New York, especially if it is not a mail-order type item.

In addition, if there are tons of widget companies, it will be difficult to get to the top of the heap in a search simply for the term "widgets". But if it is "widgets, California", then you will have a good chance of getting a high ranking if you put the keyword California prominently in the title. So, if you are in a very competitive category and your customers don't already know about you, then you might consider a title tag like this "Electric widgets from Acme Manufacturing of California" or even better "Electric Widgets in California produced by Acme Manufacturing."

Some guidelines for the title tag suggest that this tag be limited to 70-80 characters including spaces. (I confess to have used more on several occasions.)

META DESCRIPTION TAG

The next tag that has to be done is the Description tag. Many search engines use the description tag as a way to tell the searchers what the page is about. On MSN, for example, the description of the site shown underneath the title is the description that has been placed in the description tag.

The description tag is thus important in two respects: the search engine robot searches it for keywords to "get an idea" of what the page is about, and this tag will be seen by the surfers as they scroll down through the search results. If it is an interesting and well-written description then they may click through to visit the site. So this tag should be well written but also contain the important keywords that you wish to highlight.

Going back to our example of Acme Manufacturing. We could make a description tag that reads as follows: "Acme Manufacturing is the largest producer of electric widgets in California, providing round the clock service and warranties on all products." This description contains the keywords again and also says something about the company.

Some guidelines for description length recommend a maximum length of 250 characters. Once again there is no precision about this, but it is good to be cautious until you are already entered into a search engine's index.

META KEYWORDS TAG

The last of the important meta tags relevant to search engine optimization is the keywords tag. In this tag you have a chance to list your important keywords, but this time they do not have to be in a coherent phrase as in the Title and Description. Put your important keywords near the beginning. Make sure that all the keywords used in the title and the description tags are again listed. On top of that, add prominent keywords, especially those that appear in the actual text of the page you are optimizing. For the Acme Manufacturing company we could have these keywords: "widgets, widget, electric widgets, California, widgets in California, Acme Manufacturing, service, warranty, warranties."

Many pundits advise against excessive repetition of any single keyword even if they appear in different phrases separated by commas. Once again the guidelines vary and are not precise but it would be better to be conservative at first. How big should the keywords section be? 800-1000 characters is the estimate provided by some search engines and commentators alike.

The thing to remember about meta tags is that they are just one part of search engine optimization. If your text is keyword rich and your page structure allows the search engines to get to this text easily and if, on top of this, you have crafted your meta tags well, then you have an excellent chance of getting the search engine positioning results that you are aiming for.