If you are new to Sim, first off, welcome. It is a fantastic game mode and once you learn how to play it, you will find that it is very satisfying.
That being said, there is a massive learning curve when it comes to Sim.
First and foremost, if someone pings the map in your grid square, please identify yourself using the (T,4,1) method. If you fail to do so after someone pings your grid square, you run the risk of getting sniped by your own teammate. I can not count the number of times I have seen this both being the victim and the unfortunate team killer myself.