Water is evil when it is leaking into your boat. It will most often flow with gravity from the top of the boat. Drip downwards. Hit an internal hard service (like a liner), then fall to the floor and come out, making it look like it is coming down the hull sides, but it is not. Pure Evil.
Try the pressureize trick mentioned by
@Crazy Dave Condon. It works. Use a hose to spray water over small spaces on the hull, covering all areas around the suspected leak, as suggested by
@Don S/V ILLusion.
Or get inside the boat during a rain storm and sprinkle some chalk in the likely spots to see if you can track the leak back to its source. You can also try to cover the suspicious areas with plastic wrap to see if you can eliminate the fixtures.
While tracks are always a possibility, I have found Winches, hatches, ports, chain plates, and deck handholds to be the usual suspects. I discovered during the last rain that one of my port frames was collecting water. Water was wicking up between the glass and the frame due to a poor seal (air bubbles in the seal material) between the glass and the frame. The solution (cover the frame until I can properly repair it) is to create a weep hole in the frame to drain water onto the deck, then reinstall the glass with a proper seal.