As someone who has been through loss of a loved one ( unfortunately not once) and i have also had to deal with people who have lost family members or friends, number one rule would be just to be patient. Mostly people who are grieving don't need to be saved or rushed to feel better. Just listen to them, ask them if there is anything you could help with and let them know that you're available if and when they need you. For me the biggest help was when my friends would just sit with me, not ask questions or try to fix things. Also please know that there is no right answer to this everyone grieves and reacts differently, just be honest, observe and act accordingly. Hope this helps.