A scam in Project: Pokémon is commonly referred to a trade where a player isn’t given what they were promised, and this usually results as a loss of a valuable possession.

Types of Scams

Scam Description Prevention
The Leveling Scam A player will offer to level up your Pokémon for you, however, they will not return your Pokémon once they get it. Do not give Pokémon to people who you do not trust, and follow the guide on Gain EXP Faster page instead.
The Borrowing Scam A player will ask to borrow Pokémon for dealing with a Gym, and after "borrowing" your Pokémon, they will either not return it or leave the game.

There is a server message that warns about avoiding this scam.

Simply ignore these kind of people or give them advice related to the Gym.
The Dupe Scam A player would request a valuable possession (mostly Pokémon or Megastones) from you, saying that they will dupe it and then return it back to you. They can make it sound too good by offering something else if you accept their offer. Keep in mind that only Wish_z can spawn Pokémon, so what the player claims is likely to be false.
Wagering Scam A player would request for a wager battle, and when they lose, they would not compromise with giving the betted Pokémon. Do not waste your time on trying your luck on Wager Battles as most of them turn out to be scams.
The Trick Scam The player would quickly swap the Pokémon on trade with a Pokémon that you did not request right before the both sides press Trade. Inspect the Pokémon you are being offered by clicking “Info”, and when the trader does something suspicious, carefully recheck for any changes in the offer.
The Giveaway Scam The player would ask you to give them a rare Pokémon in order for you to join their Pokémon giveaway (with Rayquaza giveaway scam being most common) and once they receive the Pokémon from you, they will either leave the server or announce a random user as the winner before leaving. Just ignore these kind of people.
The BP Farm Scam This scam takes away your Battle Score, not Pokémon. A player would request you to help them with farming Battle Points, and that they would give you a Pokémon in return. After the player is satisfied with the amount of BP they farmed, they would not give you your reward as they compromised. Do not accept the offer unless you trust the person, or you could ask them to let you farm Battle Points first.
The Mystery Scam A player would claim that they know a rare Pokémon code (For example, a Rayquaza) and would request you to give them a Pokémon in exchange for it. After you give the, a Pokémon, they would either tell you an invalid code or simply leave the server.

There is also another scam that has to do with the Mystery Gift Codes. The scammer will trade you a coded legendary for one of your valuable Pokemon. Since the legendary is coded, its practically worthless.

Refer to trusted sources - such as Wish_z’s Twitter, Project: Pokémon Wiki Discord server, or the Mystery Gift Codes page - for new codes, and you wouldn’t even have to give anything for it.
Birthday Scam While not really a scam, this works by a player telling the entire server that it is their birthday. Some people on the server will fall for this scam and give the scammer Pokémon until they are satisfied. Do not give them the Pokémon unless you know if it’s really their birthday.
"Youtuber" Scam A player, claiming themselves as a YouTuber, would ask you to give them a rare Pokémon in exchange for showcasing you in their YouTube channel. After they get the Pokémon from you, they would either expose themselves or just leave the server. Confirm if the player is really a YouTuber and check if they have a history of doing giveaways for Pokémon.
The Megastone Scam This one happens when you’re hunting for a megastone from the trades. Instead of giving you your desired megastone, the Player would give you an unwanted one for a Pokémon that you offered, following the method similar to “The Trick Scam” but having two of the same Pokémon instead, each holding a different megastone. Same as with “The Trick Scam”, but with megastones instead.

NOTE: Scamming is a bad thing in the game, and you have a chance to get your save file WIPED. I recommend you not do/use any of these scams. This is just a list on how scammers actually scam. Thank you for reading this.