If you complete the catch challenges from the professors on the route, some will give you ability patches, which allow you to swap to a hidden abilities single use each.

In total you can get like 10 right now, so be careful about bad choices. I recommend looking at the extra abilities and buffs first for the Pokemon in the game because some change how the Pokemon function fundamentally.

For example: Wigglytuff is the highest base attack pure power mon currently in the game making it a physical sweeper and Ledian has a different type and almost 3 times the normal base attack with 2 punch moves buffing abilities, changing it from a screen setter like it normally is to a physical power house. 

Alternatively there are mons that have abilities that work perfectly with their hidden abilities, like the Nidos. They have Guts and Tough Claws, so you won't use them with a special set like normally, but they still get sheer force contact moves physically, so the hidden ability is worth it.