When I was a child, I could not pronounce RRRRR, and my parents took me to a speech doctor. And this is what as far as I can remember he suggested me to do, and it did work:

Quote Originally Posted by DDT
OK, stick your tongue to the roof of your mouth just about where your teeth and palate meet and try to say the letter "D" or "duh" . You will have to force air from you diaphram fairly hard at first to get the tongue to begin rolling. You want to try to obtain a continuous roll like a machine gun.
D-D-D-D-D-RRRRRRRR