Show blog posts that match a tag?

Say I have a simple blog that has a TV created for tagging, and:

The TV allows values A, B, C, and D.

blog post 1 is tagged as topic A and B
blog post 2 is tagged as topics B and D
blog post 3 is tagged as topics A and D

How do I create a query that will return all posts tagged as A, i.e. blog posts 1 and 3 but not 2?

Thanks in advance,

Jonathan

Use TvTagCloud snippet.
http://modxcms.com/extras.html?view=package/view&package=473

Are you using Ditto? If so, the Tagging extender does this pretty simply for a fixed category:

If your listing uses the [+tagLinks+] placeholder, the links will filter in the tag you click on (instead of the fixed &tags parameter].
Or you can do it via the URL query string: www.example.com/blogpage.html?tags=A.
The Tagging extender is hooked in automatically when you set the &tagData parameter.
KP
(See draft notes at http://www.pogwatch.com/ditto/ditto-extenders/ditto-tagging.html)

Thanks! I’ll give these methods a try and see what happens.