Most important factor in search engine ranking Most search engines give the title tag significant weight in displaying web pages. When a surfer types in keywords, pages that have keywords in the title will usually be listed first. Important for selling your site to the surfer From a marketing standpoint, the page title is important in selling your page. It should tell the web surfer what is on the page . Don't repeat keywords more than two or three times, or the search engine may decide you are trying to fool it and demote your page.
Search engines ignore certain, very common words.
Avoid punctuation Some search engines don't like punctuation. Try to do without it if possible within your title tag. At best they are ignored by search engines. If you have subpages, the titles should not be copies of the home page title, but unique for each subpage. In the thumbnail I have an example screenshot from AltaVista.