How to support internationalization & SEO

I have looked over a few similar questions here at stackoverflow and I can't seem to locate a clear cut answer.

I know how to internationalize my page content, but how do I notify crawlers for SEO?

Specifically, lets say I have a pages that de开发者_StackOverflow社区scribes content in Norwegian and english. Must I use multiple tags with relation to the meta "description" tag?

Also, I presume that it is good enough to add various languages to a single "keywords" meta tag as follows: <meta name="keywords" content="thejarbar.org, thejartender Java, Windows, Ubuntu, Linux, Virtualbox, tutorials, examples, guides, lærer, eksempler" /> ?

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You can simply use it like this:

<meta name="keywords" lang="en" content="keyword1, keyword2, keyword3">
<meta name="keywords" lang="no" content="keyword1, keyword2, keyword3">

But I feel better with different URL for different languages and then generating a language specific meta-data.