Making an image appear sharper involves increasing the contrast between the dark and light areas in the small details of the image. This doesn’t bring an image into focus more than you’ve already got (that’s a function of your lens and focusing, either auto or manual) but it can be a way to improve the appearance of an image, to make the details stand out to the viewer. There are several ways to increase sharpness, including automatic tools in photo editing software, but I’m interested in controlling sharpness or giving a slightly different look to my sharpening.
Here’s a method I’m working with right now. In Photoshop, create a B&W adjustment layer above the background layer. You can make adjustments to the different tones in the B&W image but I let mine use the default settings. Then make changes to the blending mode for the B&W layer until the details pop out. I’m using Hard Light and then adjusting the opacity to 50-60%. Here are the before and after versions:
As with most tools, this probably works differently on different images so your mileage will vary as you play with this method. One advantage of this method is the ability to brush on the adjustment layer mask to hide the effect on the image so you get sharpening in just the areas you want.
Landscapes, either the grand ones or the details, are usually expected to be sharp as the viewer wants to see in a photograph the same elements they would see if they were standing where your camera was placed. For best results, put your camera on a tripod and use a remote shutter release, but afterwards don’t be afraid to work on the sharpness of your images to get the desired effect. The method here is just one more item in your toolbox for creating wonderful photographs.