Instructions
Look carefully around each level as you move through the world. Try to spot crests that may be hiding in out of the way spots, such as the cul-de-sac next to the stairs in the main hall. Note objects scattered around the environment that may help you reach these crests.
Cast spells on objects you wouldn't have considered before. For example, using Wingardium Leviosa on the table, a plaque and the benches in the Tavern will give you access to a crest piece.
Finishing building objects or perform small tasks that may seem pointless at first, because these tasks often give you crests. For example, place flowers in all nine empty vases in the second world to unlock a crest.
Interact with characters using the "Action" button. Listen to what the characters have to say and perform tasks that they ask you to perform. They may give you a crest as a reward. Wave to the shop owner in the left shop window in "Diagon Alley" this way to earn a crest.
Retrace your steps if you are near the end of the level and have yet to find all four crests. Look for small clues that you may have missed, such as a portrait pointing one way or to a specific spot.