How to help someone with depression?

Help them get help. Suggest they seek help from a counselor, therapist, or psychiatrist. Listen to what they are able to tell you they are depressed about. Don't be afraid to ask if they feel suicidal, if they say yes, take them to the er, you may be saving their life.
give all the support. That is needed , and convince to seek professional help, (psychiatric evaluation and early intervention ).
Encourage consultant. Seek support? Be encouraging, supportive. Consistent, friendly etc.