How to SMILE more often and spread the smile more to others?

Smile is a friendly manner. There are two ways of smile from your face and your mind. "Real smile" must be came from mind and represent to face. A simple smile is often came from face and to do it frequently is not difficult at all. Practice moving your face muscle. However, this kind of smile is not stayed longer in minute to the one you meet.
A "real smile", you should deliver to the person you really want to care, make a relationship...In my point of view, the real smile will come up when you could keep in mind the honesty and faithfulness between you and partner. It will come when you do that.

Just give friendly smile who you see everyday!!! no matter you feel sad or happy when seeing someone. You will feel good always when smiling to peoples...Happy smiles!!

The customer looks at your SMILE even through the telephone!

from my experience, i always look at the fun side of things. That makes me smile

You have to know exactly that moment is suitable for smiling or not. If you keep smiling always, people may think you are unfitting in many cases. Sometimes, being serious may come to effect faster than smiling.
Anyway, smiling is positive to new people in normal communication. You can smile with truly sentiment if you treat people as your friends/ relatives. Otherwise, people may recorgnize the affectation in your smiling.
Your smiling will be easy to spread when it comes from your heart, not your brain. With that meaning, you don't have to try your best to make it spread anymore :-D.