How do I get my horse to soften on the bit?

Excuse me, could you please elaborate on the process of getting a horse to soften on the bit? I'm a bit unfamiliar with the terminology and would appreciate some guidance on the steps involved. Specifically, what techniques or methods can be used to achieve this, and what are some common mistakes to avoid? Additionally, how can I tell if my horse is responding positively to the training and softening on the bit? Thank you for your assistance.