Paul just moved from Moose Jaw to Ottawa, and he is not used to the use of salt on driveways. He is worried about what he should use to protect his driveway. And Greg has a driveway that keeps tracking asphalt in the house by way of shoes, basketballs and toys.
There are two basic kinds of driveway sealers:
Coal tar based -- inexpensive, and will stick to just about anything when it is hot out, including the soles of your shoes;
Acrylic based -- more expensive; guaranteed from 2 to 5 years, and will not track into the house. One catch. If you have new asphalt, or new patching material on the driveway, you should let it cure for 90 days (three months) before applying an acrylic sealer if you want it to work to its maximum capacity!
Keep in mind that no sealer lasts terribly long over asphalt, and the cheaper it is, the more it is just a quick paint job. Buy a quality acrylic sealer, and stay away completely from any tar based sealers. You can put acrylic sealer right over a well cleaned tar base. The best way to clean the driveway is to clean with a power washer first, then use an air hose to get rid of all the little stuff in the cracks. But be careful with both as they put out powerful enough sprays to carve right into the asphalt. Fill any large cracks with crack sealer. Apply the sealer on a moderate day, not too hot, not too cold. Even the pros don't do any more than that, but the cleaning out of the dust is the critical task.
When the cracks have been repaired and cured it is time to sweep the driveway clean. Using an air compressor to get dust out of the little pockets in the asphalt is a key to a lasting job. Then wet the driveway and sweep off any puddles. You may need to put primer on any stains -- unless you got rid of them with the Oil-Lift. Ideally apply a thin coat and let set for 1 hour then apply a second coat. You need to avoid rain and extreme hot or cold temperatures for 24 hours and an unusual requirement is that the sealer actually needs 3 hours of direct sunlight (UV exposure) for a good cure!
Keep your car off until completely cured -- 24 hours including 3 hours of direct sunlight -- or more if required by your specific product. Car tires can be very hot and are very heavy. If you add to that turning the wheels while standing still and you will scrub the sealer right off if it is not completely cured!