Some basic insights 

To establish the feel of a good attack,put the tongue on the reed, about 1/4 inch back from the tip of the reed.Give or take a bit depending on your comfort zone.

 To start the tone, build up wind pressure against the tongue and say the syllable "tee". Saying the syllable "tee" when starting the tone keeps the tongue arched. The consonant "t" starts the attack. The vowel sound "ee" maintains the arch and minimizes the distance for the tongue to move.

Only the tip of the tongue actually moves!!! Please remember that.

The tongue should be released from the reed precisely with the start of the air. Compare the sensation to the water in a garden hose being released. The water pressure doesn't stop when you release the nozzle; so, your wind doesn't stop when you start your attack. The attack is only established when there is continual pressure of air against the mouthpiece with abdominal support. The tongue acts as a valve, releasing and stopping the flow of air through the instrument with the pressure remaining constant (like the garden hose).

 Try this;

1.  Whisper: "he, he, he, he" repeatedly on quarter notes.
2. Change the syllable "he, he, he, he" to "tee, tee, tee, tee."

Your tongue should be near the roof of your mouth and the tip of your tongue near the tip of the reed. Work with only the mouthpiece and barrel; try to achieve a crispness in each attack. Concentrate on moving only the tip of the tongue, tonguing about 1/4 inch back from the reed tip.

 Also keep in mind; Practice at slow, manageable tempos at first. Practice "driving" your fingers ahead when you are aware they are late. Avoid the temptation to "slam" the fingers down as it cause unevenness and tension in playing. Fingers must move the same distance, slightly above the keys. Articulation will develop with time.

 Try not to do these things;

-- relaxing the air at the end of a note;
-- "gushing" air at the start of each note;
-- undefined attacks due to using an improper syllable starting the note.

Care should be taken on entrances to make sure the tongue and air start simultaneously. A big, full sound is more conducive to good articulation than an unsupported tone. No noticeable throat motion should be evident. If the throat is moving it usually means you are using too much tongue for each attack.

Practice does not make perfect.
Perfect practice does.
Do your best when practicing.
Don't just "practice" for the act of practicing.

As Sal Nistico told me many times.. " When you practice work. When you play..PLAY. " 

Hope this helps. Work hard!