My mum passed away suddenly 17 months ago. I have had a few experiences, that I will one day write about here at length. But on the whole most of my experiences in seeing my mother since she passed has been in my dreams. My mother and I used to strongly believe in our dreams and talk to each other about our dreams, so it is not surprising that this is the vehicle for communication being used. In the early months, I had such vivid and lucid dreams, that I could describe what she was wearing, and would ask her questions, including about her passing and the afterlife. Her answers were mostly vague on this subject, and I felt that I was being left to answer some of these. I have always jotted down my dreams of her which have been plentiful. It is only recently that I have not recalled some of the dreams with her in, but I think this is because of my state of mind at the moment. I know there have been dreams, because when I try hard to recall them, I can usually remember some fragments.
My mother was also a heavy smoker, and on two occasions I have smelt her particular smell of cigarettes. Once in my car, and very recently around my birthday, in my kitchen. I spoke aloud to her to let her know I knew she was there. There has been some other signs, but these were the strongest.
It is worthwhile writing these things down when they happen, so that when you feel low, and think that you are not hearing from your loved one, read over these, to remember.
Incidentally my uncle has my mums old mobile, which lights up mum, whenever he rings me. I always get that warm feeling that she's there when I talk to him. Maybe she gets him to ring me at these times.
Just look for the signs, and they'll appear. Be open, in a positive frame of mind, and think of your loved one and they will appear. Not in a way to frighten you, but in a nice way, as in your dreams.