The format for meta tags is quite simple. Your description should be less than 1000 characters, however Infoseek only goes up to 744 chars of relevance and Altavista less than 500. Keywords that appear further down the list count less. You can include one two or three word phrases in your meta keywords. When someone searches and they match your keywords, the nearest exact match will be listed first in the results.
Some search engines are case sensitive, however it is a nightmare to sort it all out.
First, you have to be careful not to spam the indexer with keywords. Search engines discount your rankings if you repeat a keyword more than 3 times in your meta tag. So if you are concerned about case of characters, you can easily go over that limit by using variations of case. A fine waste of money. I can't find a single valid reason why anyone would ever use these things.