Adding tags to your guides (or any threads for that matter) will help people who are searching for the information found within them find them much easier. This works both for search engines like google, and for the forum's search.
Anyone can tag any thread. Just click on the tags button,
Type in tags relevant to your thread. For example, if I were to write tags for this thread it would be something like this:
It doesn't take too long, anyone can contribute, and it helps out the community.
You don't need to do this for spam threads, or threads you consider minor. Just the good stuff you think/know people will want to find.
You can also look at the "Tag Cloud", which shows the most used tags on the whole website.