practice is key obviously, however if you take your tongue and touch the roof of your mouth close to where the cleft end and you teeth begins. i suppose about 2cm away from the start of your teeth.you dont want the tip of the tongue to stiff keep it loose and let the air between you tongue and the cleft do the work. the l is about the same in english. finally the ll has a similar sound to the english y for example calle should be pronounce closely to ca-y-e with a soft e sound. i hope this helps some.