Learn the three parts of the tongue used in performance -- the tip, the middle and the back. Using the tip of the tongue, make a "dee" sound and gently touch the reed with your tongue.
Practice tonguing slowly by setting the metronome to 60 beats-per-minute. Warm-up each day by playing three sets of 16th notes followed by a quarter note for a total of four full beats. Play an entire major scale, with each note using the 16th/quarter-note pattern.
Play the exercise from Step 2 at 96 beats-per-minute. Continue to increase the speed by two beats-per-minute each time until you are unable to increase the speed without sacrificing sound.
Write down the fastest speed you were able to play. Take a break and start 12 beats-per-minute slower than the previous speed. Increase the speed by two beats-per-minute and try and surpass your previous speed by 2-beats-per-minute.
Practice each day using this technique. Always start with a warm-up and then begin 12 beats-per-minute slower than your fastest speed from the previous day.