They key is to ping every second they are unseen.
I.E. Say your Mid. Laner disappears and you don't know at all where he went. Do the Triple Ping. 1 Near Top Side River Brush, 1 Near Bottom Side River Brush, 1 in the middle of lane.
Then we get fancy. If we reasonably notice our laner moving out of the Mid Lane, we ping ? ? ? ? (4x) in the last known direction the MIA enemy was missing. This gives valid warning to your Top or Bottom Lanes that Enemy X Mid Laner was moving X direction.
If we get really fancy, we ping based on move speed. Has Boots? ? ? ? ? ? Rapid succession up/down river.
This is what I do. GL.
Edit : As another rule of thumb, if it's Aurelion Sol in your Mid Lane, you just tell your team from Champ Select.. "Look fam, this fool fenna roam and I don't know if Ill keep up with it. ASOL IS ON THE MAP! PAY ATTENTION RITOPLS"