Use pings to alert teammates. As much as possible, good coordination is key to victory and pings are the easiest way to achieve that in solo games. People often don't read chat or watch the minimap, but its hard to ignore the pinging sound unless they have the sound turned off.
Use that ping to highlight the priority target in a fight.
Fall-back ping is great for calling off a gank when you can see that it will probably go badly.
I don't even type out MIAs, I quickly ping in a line leading to the lane that is probably getting ganked.
For teammates who completely ignore your warning pings, they are pretty much a lost cause. Focus on coordinating with the rest of your team.