I have come out to a few people because they asked. But how do I know when I am ready to come out to people that don't ask I.E. my family, teachers, friends, and people in my theatre group
One doesn't "know" when one is ready to do anything. It would simply be better to act on what feels right. There is no minimal level of readiness for this, there are no criteria for when it is a good time to do it, the better option is to consider what values and what philosophy of life you prefer to live by, then act in a way that is consistent with those values. For example, if you feel that living with integrity (i.e. that what is inside you is also on the outside) is an important value to you, then coming out will be consistent with that. It is fairly important to come out to those who need to know, however you define what that means, what you want to avoid is setting up some kind of wall that you need to climb before doing it, there is no wall, there is no need to wait.
So I am only out to another lesbian couple at my school as well as my two best friends, the couple figured it out from context and I told my friends without them ever asking. I'd tried to plan out how to tell them many times, and eventually I thought "screw it I'll just wait till graduation", but thats still a year away and I ended up telling them about four (I think?) months ago lol. It just came up in a moment that felt right, we were sitting outside on a really beautiful day and had been laughing for forever; it just felt right. I think what helps ease into it is the way you tell them. I basically just asked "Would y'all have any problems if I told you I think I like girls too?" and they were really relaxed about it, but we let the subject drop for a day or two before we brought it up again and I told them "So yeah, that thing I mentioned, I don't just think I like girls, I know I do." And I really think the break in between the suggestion and the affirmation made it easier for them to accept, especially my very Catholic friend who I know is still adjusting. From what I know about my theater friends is that those communities tend to be very accepting of the LGBT culture, so honestly I would bring it up with them first. It always nice to come out to people you know will accept you, and it then gives you the confidence to tell others who might take it a bit harder.