The Y-W-T Raise is a great exercise for improving your posture as it works the inter-scapular muscles between your shoulder blades, which pull your shoulders back.

Position yourself at 60 degrees on the incline bench facing forwards. Keep your legs straight and both feet on the floor for support. Using a weight in each hand make the letter shape Y for the instructed number of reps, then W and finally a T shape. During the movement, think about engaging your upper back and keeping your chest pressed into the bench. Avoid arching your lower back by engaging your glutes and keep your gaze down towards the floor.

Quite a tough exercise so start off with a lighter weight than you think you need to!