Ok.. why is it important ?

Title effects your listing:
The title of a page is how the engines list, rank and index the page. The more relevant the title, the more often they will use it to display the page in answer to a search engine query.

Engines use it as a header:
The title, is how the page is listed in search results. Have some odd ball unrelated title and it will not be indexed correctly for one, and for two will be missed by the viewer, as they will not be looking in an engine, using whatever odd words you used in the title space.

Titles are the bookmarks:
Nearly every browser uses the stated title as the book mark name.. if it's not relevant your viewer will not remember what it was about. If you get lucky enough to get saved to faves, it won't help much if they cant find you again because the page is titled, page 2 !

Your title is used as link text:
Most people, if they are going to link to your page, will use the same words you did in the title the as anchor text. If it wouldn't make good anchor text, it's probabiliy not a good title.

Too long:
Not all engines are the same..  many of them, Google for example, will cut off the title after 64 or so letters/spaces. Which means, if you have a long title you are going to lose some of it, so your wasting your time trying to put too much up there.. Plan for this and make the last words on the title, ones you can live without in case they get cut off. Better yet, is to keep it short as possible.

Not descriptive:
A good title says what the page is about. Your viewer expects to have some idea of what the content will be, before they commit to viewing it. Make it easy for them. Don't try and get clever, and call the page something like, " bet ya cant guess what's in here?" well, news, no one will even try to guess what's in there, provided of course they ever find it in the first place, with the first keywords being bet ya. This page by the way was an "about us" page. :)

There are times to violate this, as you will see on some of my art pages, the title is often the title of the art, which like many artworks, can be a little obscure. But on the same line is, Pagan Art, so the primary keywords are there and indexable, but I want the works to be known and searched, for themselves. And they are, but to a very selective viewer.

They often have their own keywords as part of the name of the artwork. Ie; Greenman, which, unless you happen to be Pagan may not mean much, but to a Pagan it's a common search word. Given, as they are my target viewer, it works out rather well. :)

Same title, all the pages, all the time:
This one is common and very un helpful, as you have given the viewer no way to know what's on the page. The engines can not index them properly either, as they are all the same. Something needs to be there all the time like the company name ?.. put it on the end of the title.. not the front.

Keywords first:
Always keywords first in line, then whatever else. Don't get too carried away with this idea however and get into keyword stuffing, a title that is a list of keywords, is just as bad, as one with none.

Ie: I have seen titles that look like this: dog,breed,breeder,sales,puppies,cats, kittens,longhair, shorthair,  then the company name. This is not a title, this is a copy of their keywords for the site overall. Wont be listed well, not helpful to the viewer as other than they are a breeder of dogs and cats for sale, you don't know what the page in question is about.

Always subject first, then what about it. This is hard for those of us who speak English, as we are not taught to think this way. We say "Let's go over to Johns house", instead of "Johns house", Let us go there. But this same, subject first, then what about it, is whats needed for the engines.

Like wise never title the page with things like Welcome to X world or whatever, it's nice to welcome your viewer but save that for the page itself, as you just set the page up to be indexed under " welcome". The same goes for " The" " to" "Hi " or whatever else as far as start words or greeting words.

Not helpful, put such things last if you must, Ie "Pagan and Proud of it, welcome to my world" , which is the title for the front page of my personal site. The two primary keywords are first and one could get rid of the "and" as engines ignore such words, but in this case its a deliberate violation as it's the site name, as well as a company name.

Hint for site design: Consider, if at all possible, that the site name and the major keywords for its over all content be the same or similar words.

KISS: Keep it simple simion.
Get too carried away with your own cleverness and you lose focus and your viewer. Use plain language and simple words. There is a limit to this however, as you can simplify it to the point of obscurity. If the page is about the "spotted leopard frog in the amazon" say that, do not shorten it to "frog" in an effort to cut down on words. The idea is, traffic that has meaning, which means drawing in a viewer that wants to know about the spotted leopard frog, not someone looking for a recipe for frog legs :)

Ditto with unneeded information, no one needs to see in the title what the url is, or what date it was made etc., ( there are some exceptions to that but they are few ) this is not useful or searchable information. Remember too, it's not just your title that is up there.. there is always the name of the browser, which cuts down on useable space.

Summation:

Keep the titles relevant to what's on the page, using primary keywords for the page where possible, keep it short and to the point, cut out unneeded information and vary the titles for each page and you should find them indexed correctly by the engines, which will draw in your intended viewer.

More soon

Esta Weiss