I know I am starting off negative - but don't tell anyone who can respond negatively if you aren't financially independent yet.
There will come a day when it's time to tell your family. That day should be when you are financially independent of them, preferably after graduating from college with a degree in something spectacular. When the time comes, here's some advice about how to do it:
Before You Even Decide to Tell Them
Don't do it on or within 10 days or so of a holiday or anyone's birthday. These things tend to upset the family more, they get bent out of shape about how "you ruined my Diwali" or whatever. They can get themselves all worked up about that and now you have to argue with them about that as well as being gay. Best to dodge that bullet.
Spend your time showing your parents how awesome you are. Just because you're gay doesn't mean that you're not a great kid who has amazing things to offer. Show them who you are, just leave out the whole "gay" part (for now). One day you'll be able to say to them "I'm the exact same person I was 5 minutes ago, but now you know who I prefer in my bed, Not that It matters since I don't want to think about what you do in bed either"
Love yourself (umm.. I didn't mean it like that, but sure why not?) Realise that you are a great person, and people do love you and love yourself for who you are.
Tell some friends who you think will be supportive first, preferably friends who don't have contact info for your family and therefore can't tell them. You want to have emotional support ready to help you cope with your family's reaction before you tell the family.
Make sure not to put yourself in a situation of dependency on your family before telling them - for example, don't get in mom's car and go on a road trip with her driving and spring it on her when you're an hour's drive from your home or car. Remember, you want to be able to stand up and walk out if it doesn't initially go well.
A Few Days Before You Tell Them
Prepare yourself for them to freak out. Be ready to remain calm and be the adult in the situation.
Prepare yourself for them to not freak out. Sometimes people surprise you.
If you can, do it in person. If you can't, do it by phone. If you're too jelly (which is legitimate), do it by email. But it's better if they have to hear your voice and see your face, because it forces them to confront the fact that it's their loved one telling them this, which makes it harder for them to reject you.
Don't take any shit from anyone. You are a person of infinite potential worth like anyone else and don't deserve to be talked down to. So if your family freak(s) out, okay, but if they start saying nasty offensive things to you or demanding that you live your life the way they want instead of the way you want or generally getting angry at you for being honest about who you are, tell them bluntly and politely how horribly they are behaving and that you expect them to act like civilised adults and respect your personhood, and if they don't shape up immediately, stand up and walk out. Don't fight, don't yell, don't act angry, just stand up and head silently for the door. Send them an email or something after walking out to let them know you're ready to speak to them when they're willing to behave like civilised adults and respect that you are your own person who they can't tell how to live your life. If things go badly, be prepared to go through a few rounds of walking out or hanging up on them and so forth before they get the clue that they're going to have to behave in order to get to talk to you. They need to learn that this isn't open for argument, you are gay and you are their family member and dems' the rules.
They'll probably have questions. Be prepared to answer any courteously phrased questions, like "how long have you known" and "why didn't you tell us". A lot of people ask "why didn't you tell me before?" ... tell them the truth, but understand that truthful answers like "because I didn't trust you" are hurtful, so if you're talking to someone who you just didn't tell because you weren't telling anyone yet, you might choose to tell them the truth from a perspective that is less hurtful, such as "because I wasn't ready to tell you, and I was afraid of how you might react." However, if they've said a lot of nasty anti-gay things, it may be necessary for you to tell them "because you a nasty bigot who replaced banter about Modi to section 377 as soon as you could" ..or something like "you say things that are very hateful and hurt my feelings a lot" so they'll understand.
Refuse any questions about your sex life or sexual practices. "That's none of your business" is a perfectly legitimate response, as is "I don't ask you what you do in your bed, who do you think you are to ask me what I do in mine?" You do not want to talk about gay sex with your family, because then they can obsess about the details of something they aren't into, rather than paying attention to their relationship with you, their family member, and how they could harm that relationship if they don't learn to behave well.
After You Tell Them
The first few people you come out to are the hardest. Don't ever think it's always going to be that difficult.
Bluntly refuse to attend any sort of religious counseling with them. Tell them no, and it's not open for discussion. " No " is a complete sentence. If they drag you into a weird stoned Baba's house about it, it's guaranteed to be an ugly scene with a possible lunatic determined to change you. If you're religious and you want to be especially nice, find your own gay-friendly place to worship at , ask the HBIC there if they'll help you with your family, and invite your family to that.
If your family want you to go to psychological or psychiatric therapy for your homosexuality, flatly refuse. Being gay is not a disorder or disease, and any psychologist or psychiatrist who treats it as one should have their license burnt to Baigan Bharta consistency. You could offer to go to family therapy with your family to help them with learning to understand you better as a gay person, but if so, you pick the psychologist to conduct the family therapy and make sure they're gay-friendly and agree in advance that the goal is to help your family learn, not to change you.
Get the contact details for the nearest chapter of LGBTQA organisation or reach out to digital counselling available here at 7 Cups of Tea or Love Doctor and talk to them about to come out to your family. Give them the information and explain that it's a group for families and friends of gay people, who are there to give them support and help them understand.
In the meantime, get yourself some therapy - if you're a working professional, your health insurance might allow for you to be able to see someone to talk to. You can decide for yourself whether you just need a few chats with a therapist or something more long term, but get some help to calm yourself down. And then go find some gay friends. You need the reinforcement of having other gay people around you so you can look at them and see that you're like them and realize you're actually normal.