Using just your mouthpiece or mouthpiece and crook you can practise your tonguing.
Practise Patterns:
Try tonguing for 8 crotchet beats then hold for 8 beats, repeat four times.
You can then double this to quaver beats, tonguing 16 quaver beats and holding for 8 crotchet beats. Repeat this four times. You can also practise this exercise to a metronome to practise tonguing in time.
Practise everyday until you can do this easily. You will know when you have mastered this as you will no longer hear the sound of the tongue hitting the reed you will just hear a nice clean sound of the note separating.