Social Engineering

I was in my favorite store today and there was a new cashier and new manager. Had to spend like 10 minutes to finish my normal transaction with lots of questions and curiosity from the new manager. However, I was able to do some small talk and get some information out of her. Reminded me of how important it is to build a good image and to maintain a good relationship with the people behind the counter.

Therefore, I was hoping to find some resources to further enhance my social engineering skills. Anyone with a good tip on how to approach and build good relationship with strangers? A good book on social engineering to read?

Thanks for any info in advance.