Using the centre focus point for a landscape image is likely to give you shots with a lot of the foregeround OOF.
You need to do a bit of research on your camera and lens and determine the correct Hyperfocal distance point for that combo at the aperture you intend to use and then focus on somewhere around that distance for maximum front to back focus.
The general rule of focusing 1/3 into the shot is fine and will work very well in most cases as long as your on reasonably level ground.
As an example, here is an image I shot just after dawn on Monday morning...
View attachment 23001
If I had used the centre point for focus on this image, the lower ground would have all been nicely focused, but the little bothy would have been OOF, ruining the image.
Remember your lens is looking at DISTANCE so if your 1750ft off the ground as I am here, focusing one third into the image would have been a good 2000ft + away from my lens, so give a little thought to the distance and dont just use that rule all the time as it will often cause you problems.
Also try and give some thought as to what you want in focus, what is your focus point? If you want something in the foreground sharp then its perfectly acceptable to focus on that and bump up the aperture to get maximum depth of field as long as your shutter speed isnt going to cause problems.
Another example:
View attachment 23002
You may have wanted the rocks in the foreground of this image much sharper than I chose, and if so, focusing one third into the image here probably wouldnt have achieved it. You would probably have had to focus on the second rock up from the bottom.
The best thing you can do is set your camera up on a tripod with the camera set up in your chosen settings. (ISO100-F11-20mm perhaps?) and then adjust the Focus point around using live view and then sit and examine the results on your PC at home and see what works for you and what the different effects are. Thats how I learnt and while im a full year into my journey with cameras now, I know I have loads still to learn, but am happy to look at it all academinally and get out there and practice. There is no substitute for taking a little advise and then just playing around with it until the knowedge becomes instinctive.