Reddit reviews The Official Soviet AK-74 Manual: Operating Instructions for the 5.45mm Kalashnikov Assault Rifle (AK-74 and KS-74) and Kalashnikov Light Machine Gun (RPK-74 and RPKS-74)

Any ammo will be fine. As for what zero works best, etc., I recommend taking a look at this and going from there. You'll learn a lot about your rifle and how it was used historically.

There really isn't much to watch out for; if you get a side-mounted optic, just make sure you know how to install one. One thing's for certain, though, clean your muzzle device and its threads (as well as the front sight block's threads it mates with) as often as possible after a firing session. This is doubly so if you're firing corrosive surplus. My latest AK purchase was an SGL 31-61 and it looks like the previous owner shot 30 rounds, maybe 60, through the rifle, but it must have been 7N6 surplus. Everything was clean but he'd never removed the muzzle device to clean it. I had to depress the detent for the device with a punch and run a screwdriver through the brake's main exhaust port area. This was the only way I could get enough leverage to rotate it free since it had started rusting. That rust was fusing the metal of the brake and the metal of the FSB threads together, effectively turning it into what would eventually become a "permanent" muzzle brake. Clean that up or it will get nasty fast. I've seen a brake that only ever saw 7N6 through it -- like 1k+ rounds of it -- that had not been properly cleaned except maybe once or twice during the first couple hundred rounds. It has been permanently rusted into place for the past five years. Only hope the owner has for replacing it is drilling out the FSB pins and replacing the entire assembly.

Keep that brake and threads clean and you'll be fine. If you don't have time/products to clean it same-day, at the very least, remove the brake from the rifle. It'll keep any rust that's forming from fusing the two items together. I make it sound a lot worse than it is, but with muzzle brakes after firing corrosive 7N6, I get paranoid. Commercial ammunition isn't as big of an issue: just keep it oiled enough to where you can still remove it by-hand and you're good.