In addition to Seasoned's post, I would say that, hard as it is, you are never truly out until you come out to your parents. It's the hardest part of coming out, and the most important one. Plan well, and bear those things in mind:
1. You don't know how they will respond, but you can predict. Are they ultra religious? Are they simple people who would adhere mindlessly to scripture, or does their religion leave space for compassion and understanding?
2. Are you financially dependable on them? Do you live with them, do they pay for your college? If you are not at least 75% sure they will still support you, even if they aren't ok with you being gay, you should take your time and do your absolute best to become independent as quickly as possible. Remember - coming out to the parents can be postponed, but it can't be avoided.
3. It took you years - for many people decades - to come to terms with yourself. Most parents - except for the most liberal thinking and accepting ones - will also need time to come to terms with it. If they are decent people it will take them far less, but don't expect a positive response right away. Coming out to the parents is never not awkward, so prepare yourself for it. Maybe they will surprise you
There are other advices - be smart about how you phrase it, be prepared to answer some basic questions if they have them, and do NOT argue about whether it's a choice, phase or whatever. NEVER argue. Make it clear that this is what it is, it has always been and it will always be and it's one thing there will be no argument about.