The tongue does not touch the teeth, it makes firm contact with the roof of mouth, pressing un the upper gums. I think my /gli/ is good enough, but many Italians are just not capable of saying it with the proper sound, it is one of the most diffucult sounds in our language. Sorry, I can't explain any better! Mr. Peachey is almost right , I would say the sound originates from the throat.

Not even close. To me, it all happens at the back of the tongue. It's just something new that you need to learn.

You can make your tongue touch the lower teeth, but this is not needed to pronounce "gli". The most important is that your tongue touches your palate, in particular the "step" before the upper teeth. The sound "gli" is similar to the L in million, try to say "illi" with the tip of the tounge still touches the lower teeth, then arch the tounge till the middle of that reaches the palate before the teeth. Have fun watching this video http://www.youtube.com/watch?v=JtlU3pMRHbU sometimes even Italians have difficult... :)