Hi, Mike. If you have fresh oil, throw down some sand or kitty litter to soak up the oil. Let this set for a day or so and then sweep it up. If you have greasy gook, scrape it up as much as possible with a putty knife. Then you can start the cleaning.
Get some tri sodium phosphate (TSP) from the paint department of your home center. Wet the driveway with the hose and sprinkle down the TSP out of the box. Let this work for a while. Scrub with a stiff bristled brush. A wood backed laundry scrub brush is OK for small stains but you will want a patio broom if you have a big area to do. Wear gloves and eye protection while you are scrubbing and may come in contact with the TSP. If you are working with the small brush, don't kneel down in the TPS. It's not real bad but it can give you a mild chemical burn. Just rinse off anywhere that starts to burn if you get any of it on you.
When you have the area scrubbed, rinse it off with the hose.