Usual applies to that which is considered normal, common, and expected: "He arrived at the usual hour." "You can expect the usual results from this medicine." Customary refers to whatever accords with the practices of an individual or group: "It was customary for us to have two coffee breaks every morning." "At that school it was customary for each girl to take her turn waiting on tables." Habitual suggests a fixed practice as the result of habit: "It is habitual for me to ignore my alarm clock." "He was a surly person with a habitual scowl on his face."
Dictionary of problem words and expressions. Harry Shaw. 1975.