What do you say after Hello?

I have always struggled with this. I am not a great communicator on a personal level and i dont know where my part is in a conversation so i usually just leave the group or say something weird to the person and say goodbye. I used to be ok at work. I once had to wait at my daughters friends place because she was out somewhere and i had to talk to the friends mum. I couldnt understand why she wanted to tell me about her nephew who called her "mum" because she looked after him while her sister in law was at work. I had no idea what to say and felt like i wanted to leave.
Is there anything to teach me how to do this?

There are probably books about the art of communication.

Using the example you gave, you were waiting with your daughter’s friend’s mom. She shared something about herself with you. She was probably just making conversation to fill the time and saying how she also cared for her nephew in addition to her daughter whom she was waiting for with you.

You might have responded with something validating that showed you heard her; like “It’s nice that you are able to help your sister” or something like that. Then she’d answer back with more on that subject and so on.

Conversation is sharing of information and ideas, connecting with others even just to pass time.

I think you bring up some excellent questions and concerns about communicating with others, Daffydungle. I agree with TishaBuv that the reason your daughter's friend's mom said what she said was because she was sharing about herself and just "making conversation." TishaBuv, good break down of what communication is!

Thanks but to me that was too personal a thing to share in our first conversation i had previously said hi before when picking up my daughter.

I usually pcik something thatbwas on the news that interested me or just bought a random non personal subject.

But usualy i dont iniatiate conversations

Maybe she wasn't for you. There's all sorts of people in the world. Not all of them make sense to us and we won't like all of them and vice versa. Its ok that you wanted to leave. There's a saying for situations like that, where its benign, but awkward: "just nod and smile."