The first 15 minutes of the movie are your free time, so do with them what you please. Could be an excellent opportunity to get to know the beautiful young couple that just moved into your house or the insanely happy 2.5 young children they brought with them, or you could just use this time to hang out in the closet (or anywhere for that matter, you're a fucking ghost!).
Whatever you do, just try and stay out of the humans' way, for now at least, because if you do start fucking with them this early, all you're going to do is make a drawer close on its own or something stupid and they'll most likely be leaving the room just as you do it and won't even notice. Save it for later.
Now that your new roommates have had a chance to make themselves comfortable, it's time to start slowly making them second guess this decision. And the key here is SLOWLY. You're not out to kill anyone (yet--mwahahahaha), you're just trying to send a vibe. A CREEPY vibe. Breathe on their neck. Ruffle the blinds. Set all the clocks to 3:33. In the middle of the night, make the basement door creeeeeeeeeeak just loud enough so they come check it out, then once they're inside, BAM! Slam it shut, just as the single light bulb hanging from the ceiling flickers out. Now you've got their attention. Unless of course they just assume there was a scientific explanation for every one of those events, which they 100% will, requiring you to up the ante in response. Are you up to the challenge?
Hey if the Partridge family wants undeniable proof of a supernatural presence, then you GIVE it to them damnit! What was that noise in the bathroom, honey? Oh gee I don't know, let me take a look. BAM! 7-YEAR-OLD GIRL FROM THE 1800's, staring at you in the mirror. What's she saying? Some fucked up nursery rhyme that calmly references mankind's inevitable mortality? SPOOKY SHIT RIGHT THERE. Honey, come back! A homeless woman just crabwalked down the attic and started vomiting all over the place! OH THE HUMANITY!
If you did your job right, your unwelcome guests got the message and hightailed it out of there faster than you can say, "Boo!" (or you know, "Dismembered fetus guts!" or whatever, this thing IS rated R, after all!), but don't get fooled: they'll be back, and this time they'll be ready. So sure, go ahead and take a load off while they're gone, just make sure you're prepared to come out even scarier and angrier than ever when they return (i.e. listen to death metal music or skin a cat or something. You're the fucking ghost, you figure it out!)
Ohhhhh shit, look who's back for more! You know what? Fine: NO MORE MR. NICE GHOST! Oh look, a crucifix! Real scary! Good luck trying to point it at me while the floorboards keep SHAKING UP AND DOWN LIKE A ROLLERCOASTER, chump! Oh hey there, Carol Brady! Whatcha got there, holy water? You know it might actually be intimidating if your body weren't currently being SLAMMED AGAINST THE CEILING by an invisible force! Mwahahahaha!
Thing were going so well, what happened? Oh no. Tell me you didn't. You did, didn't you! When you were scaring the little girl earlier you accidentally told her your horrible backstory about how you became a ghost and now she knows EXACTLY how to get rid of you! Admit it! Oh and look, what's that? Uh huh. The little red bow your mom used to tie around your hair before the murders happened. Just as I suspected. Damnit Lindsay. Okay well what's done is done. Now there's nothing left to do but cry in agony as your spirt slowly fades into the afterlife, leaving this painfully unrealistic suburban family to keep shacking up in YOUR house for the rest of their lives. Unbelievable, Lindsay. I hope you're proud of yourself!
Oh yeah LOL. Forgot you were a fucking GHOST in a horror movie and even if you die you can just come back to life later on with no explanation whatsoever and everyone is cool with it. See you in two years!