Tonguing
Your tongue is a muscle and you need to practice and work with it to get precision and perfection.There is a lot of exercises written and they are very good, all of them. But, they will not do you any good if you are not executing them accurate. The trick is often the combination "moving your fingers" and tonguing. To coordinate finger movements and tonguing is the key.

Trio Concertino
D Milhaud Suite op. 157b
Introduction et Finale (mp3)