In almost all my Spanish classes, near the end of the semester, I talk to students about their Spanish pronunciation and enunciation. It feels very silly to tell students where to put their tongue when they pronounce a "d" in Spanish and then have everyone do it.
But I notice that it is a lightbulb moment for many students. It doesn't mean that they will always be able to control their pronunciation when their minds are busy searching for words, stringing together sentences, and trying to use the correct grammar. That's already a lot to do! But many of them seem happy to hear someone explain the differences between what they do with their tongue and mouth when they say a "t" in English, for example, and what they should do when they say it in Spanish.
In the future, I may ask my students to do the modules at Prof. Gillian Ward's site, "Tal como suena." When you're at the site, click on "Modules" in the upper right, provide your name and e-mail, and then use the "Index" link to move around the modules. I found that you can't just skip around; you have to answer some of the questions before you can move to the next page in the module.
The information is pretty technical, but if you're an advanced Spanish speaker, it might be just what you need to help you sound more native-like.