(https://www.nyip.edu/images/cms/photo-articles/the-best-place-to-focus-in-a-landscape.jpg)
In a big sweeping landscape, it can be tricky to determine where to focus. For me, apps that calculate precisely where to focus is just not practical (or fun). To further emphasize the effect of the small aperture, I have found a simple solution that really works. Place your focus point on an object that's 1/3rd of the way up from the bottom of the frame and use a small aperture like f22. Not only will the object in the bottom third be sharp, but so will everything in front of, and behind it.
While F22 may be an ideal setting for a landscape, it does present photographers with a challenge especially in low light situations. Since a small aperture doesn't let much light into the narrow opening of the lens, a slower shutter speed and/or higher ISO become necessary to achieve a good exposure. These longer exposure times are the primary reason most landscape photographers use tripods.