As far as telling loved ones about your illness, for me it kind of happened organically. I am a very private person and I don't usually tell people very much at all. But somehow, it came as a huge relief when I did tell my family and friends about my depression.
The turning point came for me when I was finally referred to a psychiatrist, after a few false starts with medications that did not work and a G.P. that was pretty hopeless (although very kind-hearted).
I was frightened about seeing the psychiatrist, as in my mind, it confirmed that I was really ill and the illness wasn't something that would just go away by itself.
I rang my parents and told them and they didn't say much at all. Honestly, I can't really remember what they said.... I probably did all the talking. Maybe they were just bewildered? But I felt very relieved to have told them!
To this day, I have the impression that my parents thought that I exaggerated the seriousness of my illness and that I was only being dramatic. Anyway, we didn't really ever talk about it unless I brought it up. They just didn't know what to say, I think.
My partner at the time (who was an immature and selfish man) berated me mildly for telling my parents. He said "Why are you upsetting them with all this? You shouldn't treat your parents this way - telling them things that will only worry them." Go figure. Never-the-less, I did not for one moment regret telling my parents.
My partner was not supportive and refused to believe I was depressed and thought that the doctors were wrong in their diagnosis. He said "They are only telling you that you are depressed so as you will keep coming back to them and they can make more money from you." End of story! 
From that day on I knew I had to fight my depression by myself and that the people closest to me were never going to be of any help to me. I knew I would leave my partner as soon as I was well enough and I did. I do not regret telling him about my depression as his reaction to the news gave me an insight into what he was really like.... even though I already had a very good idea. I only wish I had left him sooner!!
I told two of my best friends what I was going through.... I told them quite matter-of-factly over the phone when I next spoke to them. One of them lived a thousand miles away and couldn't do much for me anyway, but she did listen and she did believe me. The other friend was in the middle of an abusive marriage that was breaking down and even though she showed some concern, I don't think she had the energy to deal with it. Although, she certainly never treated me differently, or anything like that. She was a good friend.
My sister was my best support, although it was obvious to me that she struggled to understand the nature of depression and it's effects on me. She kept saying " You seem normal to me." I was also very depressed as a child for a period, but when I reminded her of this, she couldn't recall it.
My sister advised me to keep seeing the psychiatrist and keep taking the meds, as this seemed like a good course of action to her. She did not treat me any differently, either, and made an effort to invite me out more often. Still, she worked full-time and had two young kids back then, so she really didn't have a lot of free time.
@Former-Member, you have to do what is right for you! I always think it is a good idea to tell those nearest and dearest to to you, as if the tables were turned, you would want to know what was going on with them. That's how I think of it.