Usually the sign is obvious. Uncomfortable and quiet as a mouse when the brehs talking about sex.
When women are around, they can be too nice.
Have higher standards and don't understand their value to women. Like if you a 5, but you got marrying 10 goals usually it will remain till you get some p*ssy which normally knocks you down to your true level. Like Joe, once he gets some ass, he gonna marry someone ugly af and be cool with it but as a virgin, he not thinking about anyone below 7 and that's typical how most virgins I met are.
Most of y'all nikkas never been around virgins in your life. Y'all used to nikkas losing their virginity in trains at 14 and shyt.
Another obvious one is heavily in the christian based church. Those tend to be the others.
Most dudes by 21 aren't virgins. Most understand the stigma and hoes too loosey goosey with their candy parts to really want not to have sex, at least if you are average or better.