I've been playing Five Nights at Freddy's 3 for a while and I've been stuck on Night 3, either killed by Springtrap or getting a game over from a phantom animatronic. I'd like to know what can keep Springtrap away, and also why phantom jumpscares are triggering game over.
You can refer to the Hallucinations on FNaF3 page on the Wiki to learn more about Phantom Animatronics. Basically, they randomly appear on different cameras for different phantoms, and most of them only jumpscare you. The jumpscares temporarily blocks your sight, hearing and deactivate some systems that would need to be rebooted. However, Phantom Mangle and Phantom Puppet may indirectly kill you. Phantom Mangle will randomly appear outside your window and emit a static sound before disappearing, which may lure Springtrap to you. Phantom Puppet doesn't jumpscare you, but temporarily blocks your view which makes the computers unusable, as well as triggering an Audio and a Ventilation Error.
To avoid Springtrap from killing you, you should avoid making sounds (such as removing the siren's sounds as fast as possible when errors occur) and lure him to other places by pressing Play Audio which will produces sound to distract him. As Webhead101 says, do not overuse it, or it may result in a Foxy Jumpscare. When Springtrap is crawling through vents, it makes some sound which you can hear and thus knowing that he is trying to reach you by crawling through the vents. Seal off the vents to prevent him from reaching you.
You have to lure Springtrap away one camera at a time. If he's in CAM 01, or the window you have to try CAM 02 and hope for the best. But generally, if he reaches there, and you aren't at 5:00 AM, you're doomed. Even if you are at 5:00 AM, you'll probably die.
The trick is to keep him in CAM 7 and CAM 8, and keep the vent that leads to you from CAM 7 closed. Some reasons this is your best bet:
It's far enough away from you that you have a nice buffer if he does get closer. You only have to worry about one vent, which you can keep permanently closed. It's not CAM 10 which has really quick access to your office. If you see a phantom on the monitor change the CAM quick. This will make it so their jumpscare isn't triggered.
Also, if he's gotten to your door quickly, you may want to consider revising your priorities for resets. My personal opinion is as follows:
Audio (You can't fend him off any other way.) Ventilation (He can sneak in when you're having your short blackouts.) Cameras (You can always guess at where he is.)