Go to the Point Reyes Peninsula. No matter which way you enter the peninsula, you will find yourself on Sir Francis Drake Boulevard, the main road through Point Reyes National Seashore. Take it nearly to the end of the road, to the turnoff for Drakes Beach.
Turn left at the road to Drakes Beach, if you arrive during the peak migration months of, roughly, December through March. The whales are so popular that the parking lots at your destination would be overwhelmed, so the National Park Service closes the road to the public on weekends and holidays between New Years and Easter. If you arrive during this time, you will need to park at Drakes Beach and ride the free shuttle between there and the main whale-watching area. Call the park service at (415) 464-5100 to see if the shuttles are operating.
Keep driving to the end of Sir Francis Drake Boulevard, if you arrive on a weekday. At the very end of the road, park your car in the lot for the Point Reyes Lighthouse. Walk down the paved (but closed) road from the parking lot to the Lighthouse Visitor Center, which is open from Thursday to Monday. Keep in mind that all services at the lighthouse are closed on Tuesdays and Wednesdays. Behind the visitor center is a viewing platform, which may be the best place to watch whales in the national seashore. It is open even when the visitor center is closed. You can also descend to the lighthouse itself, Thursday through Monday, which will get you closer to the water. There are, however, over 300 steps.
Watch for the spout of water from a whale’s blowhole, which looks just like a Yellowstone geyser. The whales may be quite close to the shore—within, say, a mile—or they may be off toward the horizon. They head south first, their migration peaking in January; during their trip back to Alaska, the greatest number of whales passes the lighthouse in March. Therefore, expect the whales to move from right to left in early winter and left to right in early spring.
Pay attention to what the people around you are seeing. This is one time when you want to be in a crowd as more eyes means a greater chance of spotting a whale. The visitor center posts the number of sightings, and the rangers usually know if a whale is in view at any given time. Your best clue, though, is the excitement of everyone around you when a whale appears.