Today someone prodded me about "what would you tell a young man hovering on the edge of gay/bi? what should *I* tell them?" I gave some answers, and then pondered.
Be grateful. Today, in the United States, is a better time than it's ever been before to be gay or bi with more tolerance, acceptance, and safety than prior generations have experienced. It's not paradise, but it's a screaming improvement over when I first came out 20 years ago, and when I came out the situation had already gotten vastly better than it had been for my elders.
It's still not a bed of roses, and there are more than a few inequalities and downright instances of flat-out bigotry scattered about, but both of us - I in my mid-40's, and you rather younger - have a lot to be grateful for, and predecessors to whom we owe gratitude.
Be respectful of yourself, your partners, your friends, and your family.
No matter what you do, you have to wake up with yourself every morning. That is much harder when you've cheated on a lover, knocked up a girl, or unknowingly passed an exciting new infection to a partner only to discover it later. Guilt can eat you alive.
When a partner confides in you, outside of a tiny number of exceptions (see: violations of law, medical sanity, etc), keep their confidence. In general, if it happens with clothes off or with them about to come off - it's private and embarrassing, and poor form to gossip about whether your partner is male or female (or they surprise you with their gender "but...I thought you were a girl/boy!"). If you're able at all, talk to your parents or trusted family friends - they can help you to avoid a huge amount of "painful stupid" by sharing their own experiences and that of their acquaintances.
Don't use sex to gross out your friends, make them envious, or any combination of the two. It's a fast path to ostracism and the return trip ain't easy. Similarly, don't try and make your friends be "just like you" - they have their own biological imperatives that will shortly become clear to both them and everyone in their vicinity, and the best course is to respect them. Only tease friends about such matters that you are *sure* know you well enough to know you are teasing and are thick-skinned enough that their fragile little psyches won't implode.
Be careful. You are worth more than your looks or your perky ass or your allegedly amazing schlong. Don't let anyone tell you different. The gay and bi male culture is wrapped up for the foreseeable future in "youth is pretty" at a near addictive level. There are few things sadder than an ignorant and uneducated "boy" that's been discarded at 20/25/30/45/60 without any discernible life skills beyond making an adequate martini. Get your education, figure out who you are, and until you do both, regard dating as dancing naked in a minefield. Don't sell out your education, your mind, or your values for the sake of anyone and "because I lurve him/her" is usually a really dumb reason - if they give a damn about you, they will be cheerleading for you to take over the world.
If you can, hold out on the getting naked bit until you have your emotional turmoil well nailed down. If not, play with partners your own age and in a scrupulously lawful fashion.
Be yourself. It won't always be cheap, but don't choose your politics, profession, or passions based on who you like sleeping with. The "because I'm gay/bi I must believe and act in a certain fashion" meme is naught but a vat of rotting and maggot infested bullshit. Ask questions, demand reasons, and always be ready to reevaluate. Who you sleep with is a part of who you are and what you like...what you like and who you sleep with is not who you are.
Learn self-defense. The world ain't sunshine and roses all the time, and it's a bummer that it's not - but you'll be vastly better able to deal with it with a black belt (which will serve you well right through high school) and later, the ability to drive tacks up a gnats ass with a .45 at 250 yards.
Martial arts have the additional benefit of keeping you all hot and sexy for your preferred partners (flab, in our culture, is rarely considered a bonus in dating selection), but if you should run into a bully or basher...better that s/he go to the hospital than you. Never throw the first punch, but cherish the ability to bring an attack to a screeching halt.
The earlier you begin target shooting, the more time you have to get good. If you are younger, by the time you can legally get your concealed pistol license, you will be scary good. That's not enough, though - you need to be scarily responsible as well. Bad things happen - to mutilate a quote "I don't care how big'n'scary a basher is...a couple of rounds of .45acp JHP center of mass will seriously disrupt their plans".
Be safe(r). No safety measure is 100% (and it's perfectly legitimate to point and laugh at anyone who tells you that they are), but you can hugely hedge your bets. Use a condom if it involves an orifice is a *good* rule, but with all kinds of enthusiasm be sure to use a condom if the proposed activity involves any orifice other than your mouth.
Get every single vaccination you can against disease, both the ones available today and ones that come out in the future - rubbing mucous membranes together can be grand fun, but it is *also* one of the more effective ways to spread the sundry diseases out there.
HIV is the big scary one that everyone talks about (for which there is neither cure nor vaccine, merely a number of varyingly effective palliatives), but the Hepatitis series is still out there and several of those can be vacccinated against.
Get prompt treatment. If weeping sores, painful urination, new skin growths, or other "gee, my body is doing something new" stuff pops up, go visit the nearest clinic *promptly*. The embarassment of getting fixed (when that's an option) is absolutely minor compared to the chat "well, guess what I found out I have...you need to go see a doctor" kind of chat...particularly and especially in a dedicated and allegedly monogamous relationship.
Enjoy. Be careful, but enjoy. Cherish your friends, choose your boy or girlfriends carefully and remember that you CAN dump them if they turn into jerks (and that if they turn into jerks, it's probably not your fault, and you probably can't turn them back into not-jerks while you're dating them). Be kind to your parents.
Meet at least one bitchy little queen. Study them hard (and they can be fun as friends, and even as lovers, on occasion) and don't become that person unless it really truly is you. Gay/Bi does not mean that "bitchy little queen" is a mandatory role, nor that civilized conduct is impossible for you.
It's not a guarantee, but look at the Gay/Bi folks that are happy and successful. Ask them how they got there. Some of what they tell you will be utter crap, some will just want to get in your pants (a bad idea), but there are nuggets of truth or experience for you to learn from - but don't forget that part of what you're learning is at least as much "dear god, don't let me be THAT stupid" as it is "gee, that sounds like really good information".
Good luck, young Jedi
Go forth and make NEW mistakes, not the same old stupid ones that so very many of us have repeated.
[Note: permission to link, with attribution, is granted to all and sundry. Quotes should likely be under a paragraph or two w/o permission - hey, I need blogreaders too! The section on safer sex was added in response to a comment on 10/12/10 that made sense - other comments were good, but I'd missed touching on that because I'd already, with the parent in question, hit that one in private conversation...but if I'm not addressing a specific person I've already covered that with, that does need to be included. ]