What should I do so that I would make a habit of smiling when greeting persons?

My question is how happy are you most of the time? I find that if I am really happy, deep down, that I tend to smile more anyway. I watch a lot of funny things on TV and I hang around with funny people so I tend to smile much more. That helps me. You can trick your physiological body to smile by biting a horizontal pencil. when you bite, it triggers the mind to think you are smiling because of the muscles that it uses. This might be a quick fix. Another thing you could do is change your thought about the person you meet. If you think that the person you meet will change your life for the better, or something crazy like that, that they are the most important person in the world and you have the honor of meeting them. You might smile, or at least grin at them when you meet them. Hope this helps

Practice practice practice. Find some time alone and stare at yourself in the mirror. Practice the different feelings from when you move your mouth muscles and when you don't (your brain may just be missing some of the signals, or picking up on some more delicate ones that don't move your mouth enough for other people to realize). Get use to what it feels like and actively tell yourself to smile at people when you walk by. Anyone. Pick a number if it's a busy place (i.e. every 5th person means you have to smile) and overdo it a little bit until you get use to it. After a while, it becomes more habit and less force.

i'm not a smiley face as well, as you can see.. but yes, i'm also friendly i just never really got into showing my emotions. and i know what you mean sometimes i think i'm already smiling and yet apparently i'm not. when i started working in a coffee shop my boss would always stand beside just to remind me to smile. that went on for a very long time and i didn't wanna piss my boss off so before i come in while i'm driving all the way to work i smile like an idiot . i think it practices my smiling muscles. after a while it just came naturally.. i've quit that job now and i don't really need to smile 10hours a day anymore but i guess all that smiling had made it easier for me to smile when the situation calls. =)

I know exactly how you feel. All you can do is start smiling and eventually it will become automatic!