How do you know if you have really seen ..?

i asked a question while reading some ones story on another topic. now i am taking it to the masses. i have seen entities for the past 10 years. not often, nor do i always know why. my friends and family have laughed it off, told me i was crazy or just think i am joking. i hate to tell them all but it would seem that i wasn't. the last time i saw anything was almost 3 years ago, just before i got married. i had moved in to my now husbands house. i didnt realize that his father had passed away there not 2 years earlier. you could see him go through the house at any time day or night, like he was looking for someone. i always got the impression that he was looking for his wife.
i wasn't the only one that saw him. my now step-son saw him one afternoon and thought it was my husband only we weren't home at the time. he is 22 so i know it wasn't the imagination of a small child. any info on this would be great help. i know i have a lot to learn and need some guidance. i just didnt know where to start looking. Thanks.