Have you checked your radiator? Is there coolant in it?

You said it's smoking.. Is the motor smoking when it overheats, or is white smoke coming from the exhaust? If it's out of the exhaust you are burning coolant. (a bit of white smoke at start up is normal, and some white smoke will come out of the exhaust when its very humid out.. condensation.)

First step would be to check your radiator for coolant. If it's full does it look dirty at all? Check your oil. If it's thick and milky your coolant is mixing with oil and you have a blown headgasket. Run a compression test to check if compression is low in any cylinders.