Offer concrete help.

If someone close to you is a victim of domestic violence, your moral support will be her best weapon, and your vigilance, her best defence. If a person confides in you that they are experiencing domestic violence, then it is important to listen without judgement, and to understand that it takes a great deal of courage to talk about it despite the shame, humiliation, and fear. Never underestimate how much your support could help her avoid future assaults.

Do something.

Offer your help.
Encourage the person to prepare a safety plan that she could use before or during a violent incident.

Be open toward the victim. Let her know that there are resources that can help her, and that you are available to talk if she needs to talk. You can also contact one of the resources that refer victims to the appropriate medical and community resources.