How many times a day should I use my inhaler?

Different inhalers. Steroid inhalers, inhalers with long acting broncholdilators (salmetrol) are different.
That depends. For those with episodic or excercise-induce, or cold-induced asthma, for instance, they may only need to take their inhaler once before encountering the condition that triggers it. Even these people should take their inhaler every four hours, if they are still wheezing or coughing or bringing up phlegm. For those with chronic asthma, they may need albuterol every 4 hours.
Depends on inhaler. There are several different kinds of asthma medication that are available in inhaler form. The most common medication is a short acting bronchodilator, albuterol. This medication is recommended to be used 4 times a day. There are long acting medications that should only be used twice a day. Your doctor should recommend how many puffs will be optimal for you based on type of prescription and your condition.