I have never been able to make the emitter solution work, though that's likely to be due my lack of skill with it.  I am in the habit of cutting the inner wall of the glass at the level I want my liquid and capping that mesh so it can be textured separately.  That way there is no issue from adjacent meshes interfering with each other.  Using the inner wall of the glass shortcuts the creation of a mesh for each container.

You can also get detailed and add a meniscus fairly easily with that method.

See http://www.renderosity.com/mod/gallery/index.php?image_id=633430&user_id=55668&np&np before my Carrara days (modeled in Rhiino) but the same method.