I go in and out of denial so its hard because the people i do talk to get conflicting information from me. I however am like you and too scared to share to much information as i am completely paranoid that i will be looked at as crazy and will be sectioned or something. I already feel like most people around me treat me like an illness first and a person second and so i hate myself when i give them a reason to confirm there treatment.
My family has been really supportive. There are some I share more with than others. I would share the broad stuff first. See who reacts best, and then share with those people more details. And the people who support you may surprise you. I was really surprised by how my grandparent's reacted. They were really supportive. I thought that with their generation, and there not really being any mental illness on that side of the family they may not understand. They wanted to know more and treated me with that same unconditional love they always had.
What I did because there is a bit of competition for information in my inlaws side of the family (nasty divorce) I sent an email out with some general information to everyone, all at once. Everyone sent back a reply of support.
It is so nice now that everyone knows. I don't have to hide. I am stable now, so that is a relief. My family has its issues of dysfunction, but they have all been great when it comes to me telling them that I have bipolar disorder.
I hope there will come a day when no one feels they have to hide. That they can see this for the medical condition that it is.
The best approach is to tell people as much as you feel comfortable with about the fact that you have bipolar and some of what occurs. Other people you know better you can tell more about if they seem approachable. Some things are best discussed with a psychiatrist. Its a matter of judgment call. That's the approach I use. I do always let people know about what my accommodations are if I need any and with people whom I trust why I might react in a certain way at a specific time. I don't share everything about myself but like with other aspects of my life it depends on how much I know the person and how comfortable I am discussing my life in general. For people who need to know informational literature and support groups such as NAMI friends and family support groups can be helpful.