Relative to your interactions with others, building trust is dependent on your core values.  These values drive how you behave and thus how others perceive you.

If you treat a promise as inviolate and behave accordingly others will observe this behavior and believe that when you commit it means you will complete the commitment in some form.

Trust

When others hold a firm belief in your reliability, commitment to honesty coupled with the ability, or strength to practice these things consistently, they trust you.

A key to creating trust is making sure others understand not everything can be treated as an absolute certainty.   However, providing assurance that you will be dedicated to ensuring everything will unfold as estimated or predicted works.

Trust is founded on the belief that you are treating your promises with unwavering attention.  Others understand while things might turn out exactly as promised mostly they will.

Before making a Promise

The key to building trust is executing on your promises the majority of the time and when failure does occur being sure it is not because of your lack of effort.

This means determining when to promise requires to advance analysis, preparation, and planning.  Without these three critical behaviors, successful delivery on a promise can be naught more than a chance.

Taking a promise lightly, without the required preparation and thus failing or succeeding by the whim of the gods can be intuitively perceived by others.

This undisciplined behaviour will erode others trust in you.  If you can consistently behave with confidence underpinned by strong planning even failure will not negatively impact the trust you have built.