I can't remember exactly when I realized it, but I found it very important to say thank you, no matter how small the gesture is, and please. It shows you appreciate what they did, and these days, this goes a long way.
I'll be holding the door open for anyone who is behind me, and I noticed more than half of the people are like robots. I watched as people pushed their way through, and not one thank-you did I hear. This was over twenty years ago, taking the Go Train to Toronto, Ontario every day to work. I worked in the Cadillac Fairview building beside the Eaton Centre Mall in downtown Toronto for a good 6 years. I loved going to work as it was something new every day considering the variety of different types of people.
I started to pay attention to everyone, and I noticed that the more money they had, the less likely they said thank you, or anything. I noticed people who asked for any extra money, change, or something like that most always said thank you. Even in stores when purchasing anything, the cashier, unless it was the owner who always said thank you so much, come back soon, you just get your bag passed to you, and they look to someone behind you so quickly you almost feel used.
Or if you go to buy furniture, unless it's worth it for that salesperson to work with you, they tell you to keep browsing until you pick out what you need. But you see the same salesperson assisting a married couple and smiling, laughing, and showing the couple everything.
My daughter and I had to find everything ourselves, and they said once you find what you are looking for, go to the cashier and ask for me. We didn't do this; we left as I personally don't want my daughter to see this behavior and think it's acceptable. I've always taught my children manners and how important it is to acknowledge people even if they didn't do anything for you.
Be respectful and responsible with your life, and you will be treated the same way most of the time. Remember that if it was you who was treated with respect, you should pass it along. You'd be very surprised how quickly the same comes back to you.