Two ways. You can go up to random people and say 'Hi, I'm a bisexual'
Or you can do it subtly. You can find a friend you trust and tell them, or you can let a little conversation be overheard (or a text message read) by a gossiper (the best people for the job). There are also many more ways of doing this.
There are no signs. If you are bisexual, no one will know for certain unless you tell them.
I would tell your bisexual friend that even though its hard to tell them but you have to because you're his friend. then nicely tell them that the other guy isn't interested and that there are better people out there for him.
'I'm bisexual'
They will tell you if they trust you. If you think you are a good and accepting friend, then they may tell you. They need to know that you will be supportive and not judgmental. They need to know if you are a gossip or if you can keep a secret.
Well, if its a guy, and he is shanking a woman while another guy is shanking him...
they find out that they're bisexual and if they think you are good friend and not a gossip or jedgemental then they will tell you i know because i'm bisexual and if anyone is gonna ask how i know this is my answer i had a crush on a male friend in yr 5 and i have a girlfriend now
If you fall in love with and is sexually attracted to both genders you are bisexual.
You can tell by the gender of the person/people you are attracted too. And if that's still confusing, you might be bisexual.
You ask her.
90% of are Bisexual.
As far as I could tell, there is no indication in any of the ten main novels about him being bisexual.
Nobody turns bisexual. If a woman is bisexual, she has always been bisexual.