For those that already know the feeling it is hard to describe. The easiest way to describe it is you just know.I'm going to attempt to give you the hard answer.
When you sense another psychic in the room with you, you feel a strong pull towards that person. You rarely have to ask the other person if they are a psychic. The easiest way to do it is if you have telepathy you can ask them and wait for the person to answer. If you don't have telepathy then you can hint around or ask straight out if you want to make sure.
Every now and then you might come across someone who will be honest with you or the will question you to see how you know. It is hard to determine sometimes whether or not a person is a psychic if there are more than one in a room.
The most common signs that a person with any ability will give you are as follows:
1. A sense of feeling that they know you.
2. A strong pull towards a person that you don't even know.
3. A person might randomly ask you why you feel the way that you do and they'll try to help if the person can.
Just be careful who you ask questions to. People are quick to judge now a days. So, just watch out for the people that might want to have you put in a psych ward.
Every once in a while you might sense someone else and you don't want to say anything because they have someone with them or they look like the just killed their parents or something on that line.
For an example lately I have noticed another psychic in my school. With purple aura coming from around the other person knowing is just elementary. Not only that but, its just a strong ignore. I don't think she is in any trouble so I'm not going to say anything.
If you want to you can give me advice on this article or on my previous article.