I agree with Carson. stretch, stretch, stretch. Use your fingers to stretch your tongue out, be creative and stretch in different directions. Thats how I did it and now kechari feels like home and I can't imagine NOT doing it. I can now easily reach the inner nostrils which really helps in pranayama. Like anything in yoga it takes time and practice but also like anything in yoga you should get results with consistant stretching.
Nice teeth by the way. Wish mine looked so good