Start off by feeling good about yourself. You can simply not be nice to others unless you start respecting yourself. Once you know how to treat yourself, simply imply the same formula for others. Put others in your shoes, and put yourself in other people’s shoes and say whatever you think will be appropriate.
Always give everyone the attention they need. This is absolutely necessary. Make sure that you are giving them all the attention they require because if they start feeling ignored, that means you are not being nice to them. The feeling of not being considered important is definitely bad and you need to somehow give attention to everyone so they don’t feel neglected.
Always try and understand the other person’s point of view. Think what you would feel if this was happening with you. And imagine if someone would say the same thing to you in such a situation, how would you react to it?
Other people do not always do what they do because they want to hurt you. At times it is a genuine mistake. In this case, always give them the benefit of the doubt. Try and understand that whatever they have done might not be their intention. Once you know that others do not always have an intention to be rude towards you, it will be easier for you to be nice to them.
Do not let your mood get in the way of things. At times you might be angry or upset about something else and while others are trying to ask you about it, you might say things which you do not mean. However, words once spoken cannot be taken back. Therefore, make sure what you are about to say and think about it at least three times before you say it.
At times you might have nice ideas or thoughts in your head but you wouldn’t act them out thinking you will do it later. However, simply do what is in your head right at the moment when you think about things.