Thanks for your response.

We have about 14,000 how-to articles on the site and it looks like only
about 4,000-5,000 are indexed at the moment. We have several thousand
more URLs that have less priority such as 'talk' pages for articles,
category pages, image pages, etc, but we're focusing on the article
pages since they are most relevant.

Thanks for the suggestion about the description. The absence of this
tag shouldn't be interfering with pages being indexed though, should
it?

Yes, there is a static link to every page on the site. Each page is
categorized and can be reached from the main page through our category
structure in 3 clicks or less, with a few small exceptions.

I've also done some analysis of our web access logs for the month of
October and it does seem like the Googlebot is reaching all of our
pages on the site, as it has made several thousand requests for main
how-to article pages in October.

One possibility is that we transferred domains from wiki.ehow.com to
wikihow.com in May, 2006. We've properly implemented 301 directs for
the old wiki.ehow.com URLs, but some pre-May 2006 articles appear to be
neither indexed in wiki.ehow.com nor wikihow.com - could these pages be
in a limbo state somewhere? If so, this would still only account for
part of our problem, there are still several URLs that were created
after May, 2006 that should be indexed that haven't been.

Here's an example:

http://www.wikihow.com/Sit-in-a-Kilt

It's a pretty informative article that was first written in July, 2006.
If one searches on Google for

site:wikihow.com sit kilt

or just

how to sit in a kilt

This page does not appear in the search results.

If you have any ideas or suggestions, we'd appreciate it.

Thanks.