I am so sorry to hear of your loss. It is thought by some that during the grieving stages, loved ones who have passed on are around more to help support us at this very difficult time.
To answer your question, there are several different ways your loved ones can communicate and you are completely right! Contact with ourselves in the physical can be attempted through avenues such as visitations in dreams where you meet with them and it feels as real as it did when they were alive, pure white fluffy feathers
(which I collect when I receive 
), butterflies, finding random pennies, robins and just like Native Spirit said, songs appearing on the radio randomly that perhaps meant something to you and your loved one.
What is most important, is that you start to be able to identify the special ways in which your loved one is trying to get through to you, look for the signs and you will just know its them
Best Wishes xx