People Friendly Environments
Like the ancient critters, the first humans to discover the wonders of the Americas had environmental preferences. They required fresh drinking water, resources for gathering or hunting food, and a landscape which fell within a range of temperatures that their bodies and abilities could handle.
Some researchers believe that there was a corrider all around the Northern Pacific and the ice margins of the glaciers.
Evidence absolutely demonstrates that people arrived in Australia 40,000 years ago. There is a model from the Arabian Peninsula that may offer a possible alternative. Over time, people moved from the fertile areas into more difficult landscapes.
If you were to live off the land, what should you do first?
Plant fiber is the most readily available resource. Nets, traps, and snares will secure a reliable food resouce when used correctly. Finding the stuff with which to make twine would be your first priority when moving into an area. Nets used in a healthy estuarine environment result in a variety of food resources.
The problem with hunting is that darts, spears, and throwing sticks (like a boomerang) require skill, endurance, an absolute familiarity with the creatures being hunted, and plenty of prey to hunt.
Therefore, I beleive that coastal areas were likely the best place for those first people to have lived because fishing would have sustained them.