Well, they are useful in many ways, not only for SEO and page ranking but these also provide search engines to explain to the public what the site is about before they click through.
The way to set up the <head> in your website in order to make the Meta tags relevant should be as follows:
Below are META tags broken down and explained:
Do your research using keyword tools, there are lots of free ones out there and list the keywords that best suit your site. Put these in, but BE CAREFUL not to put too many in as it can get too long and look like spamming to a crawler or a viewer.
This means if you have used certain characters in your text the browser knows how to interpret is and then display it.
This also appears right at the top of your browser and above the URL field.
It is important to keep the title on all the pages of your site unique and put the most important part of your title first as this has more weight of importance by the search engines.
There are other META tags available and all of them do their job in telling the browser, spiders and crawlers how to interpret the page so make sure you get these right as these have a FUNDEMENTAL affect on your site visibility and ranking.