How to help someone who's battling depression?

A close friend of mine has been struggling with depression for over 10 years now. Recently he tried to commit a suicide and ended up in a psychiatric ward. (Here's my story about it, if you'd like to know more details: http://www.experienceproject.com/stories/Am-Close-With-Someone-Who-Just-Tried-To-Commit-Suicide/4763580) To anyone who's been struggling with depression or who struggles with it now: How to help him? What to do? What NOT to do? What was/is irritating to you that people do/say? I'll be extremely grateful for any advice, my heart gets ripped into pieces every single time I watch him struggling. Thank you in advance <3