How to deal with a person with depression?

Encourage them to talk.  It will help.  Encourage them to keep a journal or diary on a daily basis.  Take them to a doctor to see if medication will help.  See that they eat a balanced diet.  Help them stop drinking;smoking;doing drugs.  Share a laugh with them.  Get them to talking about themselves.  Tell them you love them and will stand by them throughout the ordeal of getting better.  Stay happy in their presence.  Stay positive, when they complain, turn the complaint around.  Always look for the positive side of every event. 

First of all, you need to understand that this person isn't faking, they're not being lazy, they're not being a drama queen or looking for attention. A person who is depressed is genuinely quite miserable. All they can see and feel is bad. Depression is half real life circumstances and half chemical imbalance in the brain. As iy goes on the chemical balance becomes worse. The person becomes uncaring about hygiene, about everything. They simply stop functioning. It takes an immense amont of effort to do anything. It's like being at the bottom of a deep dark hole and screaming for help but no one hears you.

Be patient with them. It's true, no one wants to hang out with a miserable person when that misery is all they can talk about. But they can't help it because that misery is all they can see and feel. Be patient. Be kind. If you can, help them do a few things around the house if they've let that go. Any improvement in their situation or environment helps a lot. It's just that they're incapable of motivating themselves to do anything. Encourage them to get help, therapy and/or medication. Depression can be treated, but it's very hard. The person has to learn to change the way they think and perceive the world.

Be there for them, Don't take it personally, help out around the house and lastly Treatment is important medications and therapy are crucial to their recovery.

The best way to communicate is to empathize, listen more than talk, and ask questions like “How can I support you?” or “How can I help?”

The depression and the person suffering with depression are not the same thing, so keep them separate. When they express pessimism, anger, frustration, or sadness, it is the illness talking not the person. If you separate the two you will find it easier to cope emotionally. It will help you to be a more effective caregiver.
 Listen Non-Judgmentally
Don’t try to talk a depressed person out of their feelings, no matter how irrational they sound. This is likely to compound the problem. It is better to remain neutral and say something like “You are obviously really suffering with this. What can I do to help you feel better?” Keep your suggestions, solutions and advice for another time.
 Make a Plan for Coping with Depression
Help the person to make a plan for how to cope with depression. Identify things that trigger or worsen the depression and things that make it better. Think through and list the ideas formally on paper. Help them to put this plan into action. Some positive, helpful things to include are getting to bed early, having adequate sleep, exercising regularly, drinking plenty of water and eating healthy foods.