Most of us (including myself) on our home page tend to put "Welcome to www.whateverourwebsitenameis.com" as the TITLE tag text.
From the research I have been doing, it would seem this is not a wise practice as a good number of search engines use the title as part of their keyword search.
For example, my home page title is "Taming the Beast Online". It doesn't describe my site at all. All my most important keywords should be in the TITLE tag. I would be much better off with a tag that reads "Free Web Design Resources, online courses and tutorials at Taming the Beast".
The TITLE tag should be kept between 15-20 words and look something like this:
<TITLE>Tibetan Spider Farming resources - comprehensive free arachnid tutorials from www.yougetthepicture.com</TITLE>
- always remember to close your tags e.g. </TAG>
When you carry out a search via one of the major search engines, it is not uncommon for the results to show a good deal of "garbage" descriptions. This is because the site owners do not have a correct title tag (in some cases, none at all)...
The TITLE metatag can be found by viewing the html of your page...it is always located before the <body> tag
Remember to put title tag text on each page of your site. Most search engines don't just look at your index page. They spider the entire site. This will help increase your listings chances. Even if a user does not initially access your home page from these search engine results, they can quite easily navigate to your top page - as long as you have the appropriate links of course!
Hope this was of some use, I've convinced myself and now I'm off to fix my page!