I usually communicate with 2 regular pings, and a yellow ping. Have the pings show the path the enemy is walking, and have the yellow ping in the lane that they are headed to. No more, no less. One ping sometimes gets ignored, and I have no idea why. Any more than 3, and your team will likely get angry.
Learning how to properly ward always helps in this regard too. You might think your normal methods of warding are sufficient, but the way that you ward should change a little bit each game. Play mid often enough, and you'll find just how often your opponent wants to roam. Many people may ward their river bush, where the enemy usually ganks mid from, but you will eventually find that this doesn't cut it. The best place to ward for mid is where your enemy jungle meets the river and mid lane, next to wraiths. Keep that spot warded, and you will both know where the enemy jungle is, and where the enemy mid is. From there, you can see the usual way the mid will roam, and you can ping accordingly.
If you are not in a position to stop the incoming gank on a lane, go secure an objective elsewhere. If the mid is roaming, take mid tower. If the jungle was spotted leaving his jungle, and you aren't in that area, go counter jungle his other half of the map, or go gank a different lane.
If you have done all of the above, and your laner still dies to the gank, at that point it is just simply out of your hands, and you can know it is their fault and not yours.