Hi Richard,
Some archive pages in WordPress can produce significant traffic. Especial if the articles that reside under the archive are informative and the tag or category you use is a good keyword and provides value. So i only no index archives that have no real value.
Contact forms are up to you. Does the form sit on a landing page you want visitors? Or is it an internal link for data collection. A determination on what should be indexed or no indexed is what pages bring value to potential visitors. Many internal search pages bring no value to a user searching for your content on google. So these could be no index. User archives could be no index especial if the user is not an author of content on your site.
Thanks,
Don Silvernal