There is only one meta tag that most search engines use - the description tag. It is not ordinarily used for SEO ranking purposes, but it is usually used (including by Google) as the text on the search results listing.
The content of the description tag is used more often than not by Google when it shows the results pages for a keyword. It uses only the first 156 characters though so make sure if you are using it to check the length of the text. If you do not check the length your text will be truncated and it will look funny.
To check the length of a piece of text just paste it into a word document and then select the text and then double click the word count box at the bottom of the screen on the status bar.
The meta tags should appear in the head section of the page between the head tags.
Google is a little scallywag when it comes to using or not using the meta description tag. When it does use it you can have full control of what is displayed to possible visitors but it will often switch what it uses at will with sometimes it just picking up a piece of text from your page.
If you want to control what Google shows then the very first 156 characters of text on a page should be highly controlled because if it does not use the description tag it will use this text.
If you have a flash site or just use images with a little text, you have a problem! We have seen Google pick up the alt text from an image and display this when it didn't choose to use our description tag. This will tell you to ALWAYS have some text on your page even if it is only 156 carefully chosen characters (including spaces).
Find out more about the available SEO Singapore and SEO Trainings. You are welcome to reprint this article - but get your own unique content version here.