When I was 16 I moved in with my aunt for a few weeks leading up to her wedding. She was paying me to help with the finish-work on her house (paint, drywall, etc). It was creepy enough, it was an old victorian in the middle of nowhere in Illinois. It had one of those unfinished basements with lots of cobwebs and river-rock foundation that looked like a dungeon. Lots of creaks and noises. It didn't bother me at first and it didn't seem to bother my cousins.
One night we watched a scary movie on TV, I think it was Sometimes They Come Back. My Aunt had a little too much wine and started telling us about the ghost in the house. We all thought she was fucking with us so we brushed it off.
A couple days later my cousin Mike and I were painting the bedroom off the kitchen (old house, weird layout). We stopped for lunch and from the kitchen we heard someone walking around upstairs. We thought my other cousin Sarah came home and thought nothing of it. A couple minutes later the steps came down the stairs, and they were loud and fast (like that scene from the exorcist, but much louder). Like someone who weighed 500lbs jumping down the stairs. We had line of sight to the landing and nobody showed. We freaked. We told my Aunt and she laughed, she thought this shit was funny. We didn't tell Sarah (she was like 15 and got scared easy).
Well whatever it was moved onto her, she was in the basement getting her laundry out of the drier later that night and we heard her scream bloody murder. She came flying up the stairs and tripped on the last step, skinning her knee. She was crying and said she heard someone walking around down there mumbling. Said "he sounded upset", like agitated, but she couldn't make it out. Us kids did the laundry in pairs after that.
Welp, Mike's stoner buddy heard about this and thought it would be funny to yell at the ghosts one night. Nothing happened until after that moron went home. Sarah was up in her room with the door closed and something started banging on her door bangbangbangbang! We ran up there and her door was locked, one of those old skeleton key locks that had no way to open on either side without a key. She was freaking out in there while Mike went to get the key from my Aunt. I could see the light under the door and it cut out, she screamed for about 5 seconds, and then silence. We got in there about a minute later and she had fainted on her bed, and her shit was everywhere. Books, cassettes, posters torn down. I didn't hear anything move after she screamed. She slept with my Aunt after that.
The wedding came, her new husband started moving his shit into the house, and I had a couple nights left to stay there before going home. Everyone went over to get another load of his stuff except for me, I met a girl and was getting ready to meet her, took a shower. I had to run down and get my clean clothes out of the drier and didn't worry about the ghost (no bigger motivator to face your fears than a girl). Well, the fucking breaker tripped while I was down there. Click. Dark out. Dungeon.
I immediately heard someone scuffling around in the corner, sounded like someone practicing basketball moves on a dirt floor. I had my shit halfway out of the drier and I fucking booked. I ran right into the door at the bottom of the stairs which I know I left open. It was locked. The fucky thing is this one had a latch for the lock. A latch on the other side with the staircase. Then I heard the mumbling moving from one side of the basement to the other one the wall opposite me. I kicked that fucking door and a panel popped out (old wood door). It couldn't break the rest so I crawled through the hole and up the stairs. That was the moment I was most afraid, thinking something was gonna grab my feet. I waited outside, everyone understood but my Aunt's husband, fucker laughed at me. I wore my dirty clothes on my date, didn't matter, got laid. Awkward teenage sex. My Aunt got divorced a few months later and they moved out, lots of stress and fighting, lots of strange shit exacerbating their relationships. Messed Sarah up pretty bad.
TL;DR Ghosts like fucking with locks and turning off lights.