Dial M For Murder
It is not the only time we have heard the phrase - normally it refers to the practise of making up your own mind when using a digital camera about what bits are going to look sharp. While most of us are content to accept whatever the Auto-Focus mechanism wants to do - rather like turning broadcast TV on and sinking into the sofa - the real enthusiast/professional/geek will choose to spin the dial for themselves.
The advantages of this are instantaneous - 'cause that's what you get when you press the shutter button - the shot goes off without waiting for the camera to seek, find, and settle on a focus point and then enable all it's other electronics. If you are able to focus manually on the point where the action is about to happen, you can stop it right then.
I own three cameras with focus-by-wire technology that means the turn of the focussing ring or wheel transmits electronic signals to the motor that moves the lens. A little more fiddly than a direct helix inside the lens, but workable. As one of the cameras adapts itself to mechanical lenses as well, I can choose to go that route. In some cases - like the Leica M users, all the operation of the lenses will be manual anyway.
If your camera supports this method of focussing, look further into its specifications and see if it has a feature called " focus peaking ". This is the ability to show a rime of bright highlight in white or a selected colour around objects at the plane of focus. It makes accurate manual focussing easy in dim light or in close-ups.
Do not think that I decry the AF of the modern camera. It saves your bacon most of the time when it comes to getting an accurate sharp image but remember that some dishes - like ice cream - are better without bacon.