Use a Sturdy Tripod.
Use Manual Focus
Focus Manually With the Live View Setting on your camera. To do this you’ll first need to switch off the auto focus setting on your lens. Next you’ll switch to Live View. Once you’ve done this use the magnifier box in the screen to punch in on the subject at the furthest distance. Then slowly turn the focus ring on your lens until that subject or object is pin sharp.
Shoot Using Your 2-Second Timer
Use the 2-Second Timer setting on your camera to minimize any possibility of camera shake caused by vibration when you press the shutter. If you’ve got a shutter release cable you can use this instead.
Enable Your Mirror Lock Up Feature
If you’re using a DSLR use the Mirror Lock Up feature to prevent any possibility of vibration which can occur when the mirror flips up into position as you take the exposure.
Use the Lens Best Aperture Setting
Find that Sweet Spot Aperture value of your lens. Most lenses will generally have an aperture value which will guarantee maximum sharpness throughout your image from foreground to background. This is usually between f/8 and f/11.
Focus at infinity.
There are several theories how to achieve maximum sharpness by using techniques such as calculating Hyper-Focal Distance. However I have found that by simply focusing at infinity I’ve been able to achieve maximum front to back sharpness throughout the scene.
Turn of Image Stabilization
Switch of your lens Image Stabilization or Vibration Reduction. If your lens has any Image Stabilization or Vibration Reduction you’ll want to switch that off. Unless you’re shooting hand held using any Image Stabilization feature can result in a soft image due to the lens correcting for camera movement when it’s already on a tripod.

Bonus Tip to greatly improve your image quality.
Use the lowest ISO setting.