Once you have your clarinet, or clarinets, there are a few other essential accessories to acquire. The cotton pull-through is used after playing to dry out the condensation inside the instrument. Cork grease lubricates the cork at the joint ends (or tenons). It will sometimes be necessary to visit a clarinet repairer, for instance to replace worn pads. Occasionally it helps to look up and down the instrument to see if there are any loose screws which should be tightened. The general approach should be: handle with care because the clarinet is delicate.
The clarinet needs constant practice to in order to maintain your embouchure and technique. The embouchure (from the French 'la bouche' for 'mouth') describes how the mouthpiece sits in the mouth. This also includes the position of the resonating cavity of the mouth, jaw and throat. The lower lip is tucked over the bottom teeth and rests against the reed, like a cushion, and the top teeth gently press down on the mouthpiece (having a mouthpiece patch here is a good idea). A small number of players also put the upper lip between the top teeth and the mouthpiece resulting in a 'double lip' embouchure. Aim for a firm but relaxed embouchure and an 'open' inside resonating cavity.
Diaphragm control (the diaphragm is a flat muscle which sits beneath the lungs) is an important aspect of clarinet playing and should result in a controlled release of air being 'pushed' through the clarinet. One of the best exercises to practise diaphragm control and embouchure is to play long notes (around ten seconds) of various dynamics and pitches with the emphasis on producing an unwavering, focussed note.
Finger technique will inevitably develop by playing studies, scales and arpeggios, and pieces. A crucial thing to remember is to try to keep your fingers relaxed, which means the rest of your body needs to be relaxed.