Meta Title tag is one of the most important ranking factors in the search engines ranking algorithms, so populating your most important keywords in this tag will dramatically increase the search engine rankings of the page.
Rules for Title tag:
1) There should be 10 to 65 characters including spaces. Try to minimize the use of stop words, such as a, an, of on, etc; as they consume character count and offer no value. The Title tag should be unique for every URL and with well targeted keywords for respective web page.
2) Keywords have to explain about that particular page content and they should not be stuffed in any manner.
3) If you think that the length is insufficient, then you can use at least 70 characters. Over 70 characters it will not be contributed at any part of the document.
Meta Description tags are not made for search engines, they are made for humans. So write a text that sells to convert the searcher into a buyer, and achieve the best return on your search engine marketing campaign investment.
Rules for Description tag:
1) There should be 60 to 165 characters including spaces. Google displays 154 characters, but other search engines display even less characters.
2) As with Meta Title, description should also be unique for every URL on the website.
3) Description has to explain about that particular page content and you can also provide an opportunity to feed long tail keywords. This can provide potential visitors and can increase the ‘Click Through Rate’ [CTR] from the search engine results.