How do people build deep connections with each other? Like how do they know the right things to say in conversations?

When you know what to say to that person to make them happy , and to make them laugh , to think , to smile..8) when you know all that the connection is already there..the words just fly out..8)

Best way is to be yourself, honest, faithful, tell your companion what the things you expect from this person are. Good communication always works. Remember that every person is a different world but if you are open & of course without disrespecting yourself you will be able to have a long relation. Do not think that you own the other person and act the same way you did when you met this person