Writing Tip #2 - Do Your Research!
James laughed as he charged after Sirius through the corridors, their chase being witnessed by irritated portraits as they ran. He could hear Filch's shouts echoing after them, catching up even, and the sound of Mrs. Norris's paws was even closer. James was exhilarated.
"When the bloody hell did you get to be so fast, you mutt?" he panted as he put on a burst of speed to come alongside Sirius as they turned the last corner, the tapestry coming into view.
Sirius grinned, turning so he was running backwards, purely for show. "I've been taking laps about the woods every full moon, Prongs!"
"Training to be the fastest arsehole ever, are you?" James asked as the boys reached the tapestry.
"I haven't got to be the fastest arsehole ever, just faster than you!" Sirius ducked into the secret passageway, holding back the curtain as James joined him.
"So you do admit that you're an arsehole, at least!" James hissed as the tapestry fell back into place, concealing them from the eyes of Filch and his cat.
Sirius only grinned at James through the dark, knowing any noise might give them away.
The sound of Filch's footsteps came trotting unevenly down the corridor. His legs were getting tired, they probably could've out run him altogether, even without the passageway, by the sounds of it. "BLAST!!!" Filch shouted as he came to a stop. Mrs. Norris let out a frustrated mewl. "ALWAYS IN THIS CORRIDOR! I always lose them here!!" His voice was rough with frustration.
James and Sirius had to cover their mouths to keep from laughing.
The sound of Filch once again tearing apart the corridor echoed and they quivered with mirth as helmets on the armor clanged and portraits voiced shouts of indignation as Filch pushed at their frames, trying to find evidence of a hiding place. The old gnat never thought of looking behind the tapestry - surely if they were there they'd show, he reckoned. Their feet below and the curve of their bodies in the fabric. It was always an absolute thrill to stand just there, just out of sight, and listen as the old man bluthered about in frustration that they'd managed to escape so seamlessly. So long as they didn't make any noise, they were safe...
That's when Sirius's cellphone rang, the sound of Freddy Mercury's voice blaring out from his pocket. "MAMAAAAAAA JUST KILLED A MAAAAAAAAAN.....!"
"Blast!" Sirius shouted, scrambling to mute the phone, even as James launched himself down the hidden corridor and away from the tapestry, which was torn open, revealing Filch, who grinned wildly.
"AHA!" he shouted.
Sirius looked about, surprised to find James had scrambled away so quickly, leaving him alone to face Filch.
"Too bad you didn't listen to my notice about muting your cellular device!" Filch jeered as he reached out and grabbed Sirius by the wrist, firmly pulling him out of the secret passageway. "You'll be suspended for sure for this! Oh what a happy day! A happy day for Argus Filch!"
Poor Sirius. Caught by Filch - earning himself several detentions of hand-scrubbing the Prefect toilets for all four houses while Filch set himself up with an iPad and made a good time of playing Candy Crush while Sirius grumbled.
All of Siirus's woes could have been solved by a simple inquiry on Google....
Did cellphones exist in 1975?
Do your research. It could save a Marauder's life. Or at least a few Saturday afternoons.
Do your research! Don't assume things were the same in your story's setting as they are in yours.
Research the year, be mindful of technology. Be extra mindful of technology in a fanciful setting4 like Hogwarts. Elekytricity isn't even a thing there!
Look up release dates for songs. Be aware that a lot of the songs Siriud would listen to would be new releases. Make sure you know if a song he is quoting has been released. Hint; make sure you specify "in the UK" when you search this one as different countried often have separate release dates than the US!