This h sound is more like a "wh" sound, as in "who, what, where, when, why." However, so many of my students end up saying the "huang" or "xi huan" with a "g" or "k" sound. So "xi huan" would sound more like "xi guan" (shee gwan) or "xi kuan" (shee kwan), while "huang" (hwong) sounds more like "kwong."
I have tried numerous time to use the "who, what where..." comparison to help them pronounce the words correctly. In fact, for my younger students, I make them repeat those words after me: "Who, What, Where, When," then followed by "huang" or "huan". Most of the time they are able to say it correctly after that, but when I have them put that word into a sentence or phrase, they revert back into the "g" or "k" starting sound again. Obviously if the can repeat the correct sounds back to me, then they are physically able to hear and make the correct sounds. However, it's a matter of helping them remember to actually make the correct sounds consistently, and somehow, they really have a challenge remembering the correct pronunciation.
Have any other Chinese teachers out there encountered this issue? If so, what methods do you use to correct your students' pronunciation or to teach them the correct pronunciation?