The State of Alabama places few restrictions on collecting fossils. The landowner's permission is required to collect material from private land (and most land in Alabama is privately owned). Human remains and artifacts may not be dug out of the ground, although arrowheads can be collected from the surface. Nothing may be collected in caves except for scientific purposes. Finally, the State Fossil, Eocene whale Basilosaurus cetoides, may be collected, but specimens may not be removed from the state without the written permission of the Governor.
The federal government requires a permit to collect fossils on federal land, such as national parks and forests. However, most federal land in Alabama is relatively nonfossiliferous.
These restrictions are not burdensome. Alabama has many roadcuts, railroad cuts, and river bluffs that are accessible to the public without special arrangements. And most landowners are friendly to fossil collectors as long as they do not damage the property or scare the livestock. Many landowners will actually lead you to the best places to collect. Remember to close all gates and do not dig holes unless you have obtained permission first from the landowner.
Dealings with landowners can be improved if you talk with them about your goals for the visit. Most people are keenly interested in human artifacts and vertebrate remains rather than shells, so landowners are often friendlier about letting people collect shells than arrowheads or bones. If you are out hunting shells, let them know. And it never hurts to send a note of thanks afterward.