Title, keywords, subject and description are a must for search engines submissions. Author name is highly recommended. Charset and language are useful only if your page if not standard English. Distribution and expires... well... there is more than one opinion about these tags, I would leave them empty, but if, for some reason, you want them, here they are. Some experts recommend to include author/contact email. In my opinion that's just invitation to spammers, so if you don't have a very good reason to put here your email, better leave it empty. Most of the time you don't need Robots field. So that's it. Fill what you want to fill, press button and get ready tags! Good luck!