How can I make sure mother gets her legal share in father's property

My Father was died and i with my mother are practically driven out from our parental family. So, till now not any share of property or in any term provide by the in laws of my mother. We don't have any information about it also because we are living in different city. I just want to ensure that all the legal or proper share of my deceased father has to be given to my mother. If not so atleast assure that in-laws of my mother will not make any transaction in these property till the full and final settlement. So, what should i do for it and also please suggest me the positive checks so any kind of wrongful action not done by the in-laws of my mother.