You can check the difficulty of a raid while it’s still a egg; five-star raids have five little monster icons, Mega raids have the Mega DNA-like swirl, and shadow raids are at gyms taken over by ...

After that, face a couple of 4 and 5-star difficulty raids and you should be good to go! Start by finding the raid den for the desired Pokémon, it’ll be a dark, black flashing icon on your map.