The Resident Evil 4 Remake Blue Medallions work a little differently from how they did in the original game. Back in 2005, you'd have to locate all of these Blue Medallions yourself and shoot them to get the special Punisher handgun, which is capable of shooting through those annoying zealot shields, or multiple enemies, if you line them up in a neat row.
While you still have to shoot the medallions in the remake, they now give you Spinels for trading with the merchant, and you don't have to locate every single one yourself—great news since there are absolutely loads of them. So if you want a few extra Spinels but an easier way to locate each Blue Medallion, here's what you need to do.
How to find the Blue Medallions
Unlike the original Resident Evil 4 where you had to locate all of the Blue Medallions yourself, you can actually just get them marked on your map in the remake. All you need to do is pick up the relevant request poster and it'll give you every Blue Medallion location. In the Farm area, for example, go and pick up the request by the locked gate before trying to track down the medallions yourself. It's the same in chapter seven when you're trying to break into the castle using the catapults: you'll pass through the area with the Blue Medallions before you find the request that gives you all of their locations on your map.
That said, even with their locations there are a few medallions that are a little tricky to track down. The best method is generally to face a medallion marked on the map, and if you can't see it, try looking up to see if it's hanging from some distant structure, or looking between pillars. Shooting some of the last ones requires a very precise line-of-sight, meaning they are only visible when you stand and face in a certain direction. It's also a good idea to bring a scoped rifle so you can pick off those trickier ones with ease. Once each request is completed, bring it back to the merchant to get your Spinels.