META Description

A meta description tag is suppose to give a brief description about your website. It should represent a concise summary of your page content. When you write a meta description for your site make sure they are not more than 170 characters. You should pick a style for writing your page description and be consistent throughout your website.

Some tips for writing good meta description:

Always start with capital letter
Its good to have a sentence structure, but fragments are also acceptable
Make sure there are no spelling errors in your description
Try not to repeat the same word or phrase
You must not enter a list of keywords as your description
Use of shorthand in description is strongly discouraged

META Keywords

A meta keyword tag was originally designed to let the search engine know about the keywords of your site. But nowadays, many search engine including Google, Yahoo and Msn doesn't use this meta tag to determine your site's keyword. They use more advanced and complex algorithm to determine the right keywords for your site. However, meta keywords are still important for many search engines, web directories, and those who still takes this meta keyword into consideration. The meta keyword tag is meant to provide a short list of the most relevant keywords on your site. Please make sure that you can narrow down your keywords to 10-15 words, else it is very likely that your page content is not structured and contains too many unrelated information. For example, if your page has the following words 'loan' andinterest rates', does it mean that your page is about loan? Of course Not! It can be a page solely about selling cars and some little information about car loans.

Some tips for writing good keywords:

Don't include more than 15 keywords
Choose only relevant keywords
Never use keywords which cannot be found on your content
Do not repeat any words or phrase
Put the most important keywords at the beginning

Though META tags are not very important factors in determining your page rank and search relevancy, but still it is the very basic SEO technique for any website and must be followed correctly. All meta tags other than meta keyword and meta description are obsolete now.