You have probably heard of cold reading and this sadly is what some so called psychics/mediums do. They read you and your demeanour.
Unfortunately, there are lots of fakes out there. As in all areas of life, there are those who do not have the gift but pretend to, in order to show off, or even worse, to cheat you out of your money. There are many people who make money from the misery of others. These are not spiritual people and this is why you need to be discerning about who you go to see for your reading.
Cold reading is one way some people work. Guesswork is not far behind it. Also, gossip can be used and embroidered upon to make up a supposed message, by some ignorant beings; those who should know better too.
A true medium would never stoop to such levels, and it is here that the need to prove life after death is important. A cold reader cannot tell you anything that could prove life after death, or anything about loved ones in the spirit world. A true medium is needed to contact the spirit world and get real proof for you.
A cold reader is someone who studies your body language and facial expressions whilst they are speaking to you. They look at things like wedding bands or the lack of, and for signs that you may have stopped wearing a ring. They observe you to see if you are nervous when certain subjects are mentioned, and play on the subjects where you are more responsive. They will also most certainly ask you probing questions and do what I called ‘fishing’.
Unfortunately, even in a Spiritualist church there can be cold readers, fakes, and the downright self-deluded, although church committees on the whole try hard to deter these kinds of people.
The moral is, only go to someone who has been recommended to you for a reading. That way you will know they are genuine, but you should still not offer any personal information before your reading.