Metroid Prime 2: Echoes is a Metroidvania-style game, meaning extensive exploration and backtracking with new abilities are core to its design. When you acquire a new upgrade (e.g., Boost Ball, Spider Ball, a new beam), make a mental note of any previously inaccessible areas that might now be open. The map system is your best friend; areas marked with a red square often indicate a locked door or an area you haven't fully explored.
Use the Scan Visor liberally. Many hidden passages, weak points in walls, or interactive elements are only revealed through scanning. Look for subtle environmental clues, such as cracked textures or unusual energy signatures. Don't be afraid to experiment with your Morph Ball abilities in seemingly dead-end rooms; many secrets are hidden behind Boost Ball jumps or Spider Ball tracks. Efficient backtracking saves time and ensures you find all collectibles.