Exploration is key! While the island does change as you progress further into the game's story, landmarks will continue to remain where you initially saw them.
When a bear asks you to find an object, they will give an approximation of where it might be located. For example, they might tell you that it's near a fountain, a telescope, or maybe an equipment shed. You can view these tips by clicking on the object in the journal.
If you have spare coins though and want to easily find hidden objects, go to the Hint Dispenser, click on the "Get hidden object directions." option, then select the hidden object you want to find. The Hint Dispenser will point you towards where the hidden object is exactly located.