There is often a move to stuff as many metatags onto a page as possible but it is really not necessary to include copyright, author, contact info, etc. metatags as you should include these in the visible part of your page. The important thing to bear in mind is that search engines rank the relevance of your content based on where the keywords appear in the source of your page; large quantities of metatags push your content down the page and make them less relevant, so use as few as you can get away with.
These are the general ones that I always add to most pages I do:
quote:<meta name="description" content="This site is......" />
<meta name="keywords" content="Keywords go in here" />
<meta name="abstract" content="This is a short version of description." />
<meta name="revisit-after" content="7 days" />
<meta http-equiv="content-type" content="text/html; charset=utf-8" />
<meta http-equiv="window-target" content="_top" />
<meta http-equiv="imagetoolbar" content="no" />
<meta http-equiv="MSThemeCompatible" content="no" />
And they mean:
Description: A longer piece describing the site. This and the following 2 meta tags are now increasingly not included in the search engine's algorithims but it does no harm to keep them in - just don't spend days worrying about them
Keywords: List of keywords about your site (they can be separated by commas but current thinking suggests its best not to use them and allow the robots to work out the phrases).
Abstract: A shorter version of the description - often a good way to sneak extra keywords onto your page.
Revisit after: Tells robots when to return to your site (other robot-focused tags, like the robot tag, aren't reuired if you want it to index everything and follow all your links as that is the default behaviour anyway).
Content type: The language encoding on the page. (See the Relevant FAQS section below for more information.)
Window target: Breaks you out of any frames and avoids having to use JavaScript.
Image toolbar: Turns off the IE6 toolbar which appears when someone using that browser puts it over your image. Looks messy and can promote casual theft (even though it is very easy to steal images anyway, lets not prompt people to do it ).
MSThemeCompatible: Stops Windows XP from taking control of some of your page elements and styling them which can make your pages look messy.
You should also consider using ratings meta tags (see below).
If you recommend any other tags then add them in below (with an explanation):
If you are using HTML 4 and are including CSS and/or JavaScript on your page then you should consider these other encoding metatags:
