Below you will find several tips to achieving maximum sharpness. This list is not meant to be an all-encompassing list but a good starting point nonetheless.
A good base is essential.
You have to have a sturdy base. If you are moving around, it’s hard to get get the sharpest photo you can. I know you’re asking how do you have a good base? Well if you played sports you know that a good base does not come by having your feet together so spread them out about shoulder width. Usually one foot slightly in front of the other. If you can lean on a wall or pole that always help. I also prop my support hand up on torso, especially with heavier lenses.
Know your lens.
Figure out what the sharpest apertures for the lenses you use are. Usually, this is in the 7.1 or 8 range, but that is not always the case. A quick google search will give you this information. You can also test your lens if you want.
To do so get a newspaper or piece of paper with print on it set it up at the distance that you commonly shot and use similar light. Put your camera on a tripod and if possible use a cable release. If you don’t have on you can use a three-second delay, also if you are shooting with a DSLR lock the mirror up to reduce vibration. Then shoot several images at different apertures starting at your lowest and working your way up. For example, I would start at F/2.8 then progress down to f/4, f/5.6, f7.1, f/8, f/10. Then compare to find your sharpest aperture. With all that said I know a lot of photographers always shoot wide open and get great results.
Don’t zoom to the far ends of your lens. On a 70-200mm lens shooting at 180mm will be sharper than 200mm and 135mm even sharper than 180mm.
Nail your focus.
Always focus on your subject’s closest eye. Just like in golf aim small miss small don’t just pick a spot on the person you are shooting select the nearest eye and focus there. Doing so will help ensure you have the best possible focus thus achieving maximum sharpness.
Easy on the shutter.
Don’t mash the shutter button! The correct way to depress the shutter button is to roll your finger across the button. I have watched people mash the button down so hard that you can see it move the camera. Also on some of the consumer line cameras and even my FujiFilm XT2, you can upgrade the shutter button to make this process easier for very little money. Here is a link to the ones I use on my Fuji’s.
Bonus tip.
Do your sharpening last in your workflow. You should sharpen for the medium that your photo will be displayed or if the picture were small or large. For example, a shot that that will be printed on matte paper will need more sharpening than a picture that will be viewed on screen or glossy paper.