What are the tips on training a horse to canter?

Teaching a horse to canter correctly — to depart on the correct lead, maintain the gait willingly without breaking down, and carry himself in a balanced three-beat rhythm on both leads equally — is one of the foundational achievements of early training and reveals the quality of everything that preceded it. The canter departure is not a separate skill taught in isolation — it is the product of a horse that is genuinely forward off the leg, supple enough to bend correctly in both directions, balanced enough to organize himself at the moment of the ask, and responsive enough to depart from a clear light cue. Confirm the walk and trot are genuinely correct before introducing the canter. A horse that rushes at the trot, falls on his forehand, or ignores leg aids will have significant canter problems regardless of how the canter is taught. The canter requires more balance, more collection, and more hindquarter engagement than the trot, and a horse that cannot manage those qualities at the trot cannot manufacture them at the canter. Corner geometry is the most practical tool for teaching the first canter departures. Asking for the canter as you come out of a corner puts the horse in the optimal mechanical position for the correct lead — the natural bend of the corner has already loaded the inside hind, the horse's weight is already slightly shifted in the direction of the intended lead. Many horses that struggle with departures on a straight line will produce clean, correct departures out of a corner with very little additional help. The cue needs to be clear, consistent, and applied the same way every time. The classical western canter cue involves sitting a beat of the trot, shifting weight slightly to the inside seat bone, applying the outside leg slightly behind the girth to ask the outside hind to initiate the lead, and keeping the inside leg at the girth to maintain bend and forward energy. Apply this as a complete coordinated package rather than sequential pieces. Both leads need to be developed equally from the beginning. The harder lead needs proportionally more work than the easier lead to develop the strength, suppleness, and balance that makes both leads equally available. Do not avoid the harder lead because it is inconsistent in early stages — consistent correct work on the harder lead is what makes it equal to the easier lead over time.