Practice! If you develop asthma symptoms with exercise, you may need to use a bronchodilator pre-exercise and have it available when you stop exercising as well. See your doctor if you have symptoms with exercise so you can be treated. Exercise is good for asthmatics and there is treatment available to allow you to exercise!
EIB vs Asthma. First, it is important to distinguish between eib (exercise induced brochospasm) and asthma. You can have both, but if you have asthma, merely trying to take a bronchodilator like albuterol before exercise will not be sufficient. If you have asthma, you must get the underlying inflammation under control by taking a daily controller medication such as singulair (montelukast) or flovent. See your doctor.