Old school shooters:
Don't fucking wait for seargent McDude to open a fucking door while he talks inanities about evil russian terrorists.
Don't fucking stay glued to the ground while shooting over hordes of defenseless enemies on forced turret sections.
Don't fucking shoot the same ruskie evil terrorist, Alahu Snackbars or Dindus from the start to finish, variation on enemy types and enemy placement is crucial.
Don't make enemies that you headshot with a .50 cal machinegun to the head and they just fall on the ground as if nothing happened as if they died of an heart attack, you shoot dudes, there must be feedback. Half the fun of shooting on real life is seeing the damage you've done, same on games.
Shitty arenas with hundreds of enemies doesn't make a shooter old school, level design is crucial, good level design allow for smart use of enemies to surprise the player. If you make shitty arenas over and over, the gameplay will start getting boring and stale pretty quick.
Don't make the player to wait hidden behind a corner like a little bitch while his health recovers, if he is a scrub and can't avoid shots, he must start learning or give up on gamming, fucking carebear idiots should euthanize themselves to make the gene pool better. If you wait behind cover, you aren't shooting or moving and this break the pace of the game.
Levels must have a theme and look like a real place, even if highly abstracted, you are fighing on a strip club, you are fighting on a demon infested hell base and no, only idiots use their imagination to do the job of developers after paying them 60 dollars, I won't imagine the corridor, intestine level I'm playing it is more than a gamey corridor, lazy intestine level. Im not fighting on a military base but on a Disney railroaded theme park.
Enemies shouldn't have only hitscan weapons and be able to murder you if you don't hug your nose to a wall, circle strafing bullets isn't realistic but regenerating .50 cal wounds isn't too but the former is much more fun than the latter.
Health packs are good because they stimulate the player to avoid getting shot as the player has to make use of a limited resource while giving him some room to make some mistakes. Fucking adding medkits that heal your whole health on every fucking room isn't much better than waiting for the health to regenrate, med kits on thmselves don't make a shooter old school, only if the medkits do their supposed mission of being a limited resource.
You are a circle strafing killing machine, killing armies, the gameplay on most first person shooters is silly, if your gameplay is silly and over the top, don't try to make the player to care about serious stories, the FPS genre was better when they all had that 80's style dumb action movie. Trying to make you care about the horrors of war after you killing a fucking huge enemy army alone doesn't work.
Rule number one: Don't make a game for the consoles, gamepads weren't made for FPS, people still insist using them for this function for some reason, maybe collective retardism, no, making your game slow as shit so gamepad fags can play them is dumbdown, doesn't matter how you try to spin it.