If you are not eligible for overtime, you must receive compensatory time off (comp time) at 1.5 times the rate of hours worked beyond 40 a week. Period. "Exempt" employees are only exempt from being paid overtime in cash. The manipulation and studied ignorance of the Fair Labor Standards Act by management is one of the biggest scams going.
I have seen one guy making $250 a week who believed he was not eligible for overtime because his employer put him on salary, and designated him as "manager" - of the firebox at a barbecue restaurant. He worked an average of 50+ hours per week, but his employer assured him he wasn't entitled to OT because he was "management," and because if he ever worked less than 40 hrs in a week he'd still get his $250.
I have seen people who believed that they were lawfully on salary at $X per week, no additional pay for time over 40 hrs, but docked at a specified hourly rate for time under 40 hrs in a week.
You are entitled to either time-and-a-half for OT, or comp time; you must be paid your regular salary while using comp time. The way employers abuse this crap chaps my ass.