Instead of blocking them with robots.txt (which isn't very effective), try using the canonical tag instead.

For instance, a URL like this:
http://wwww.testdomain.com/page.html?utm_source=Google&utm_medium=Banner&utm_campaign=Campaign

You could add this canonical tag in the head:

With this solution you don't have to worry about losing quality links OR having your query tracking show up in any of the major search engines.

Cheers- Kyle

As long as you have the correct syntax and it is all in the of the document there is no negative or positive effect on the positioning of the META elements in regards to SEO.

As for the best META elements to include for an SEO benefit - that would be your title and description tags.

Hope this helped! - Kyle

Check out this page, about half way down in the article: http://www.tamingthebeast.net/articles3/spiders-301-redirect.htm

They cover both dynamic query pages and pages with spaces.

Good luck - kyle