Treat all people nicely
It is a great thing to treat all people around you nice. It is not enough to only suck up for bosses and people that are upwards on the corporate ladder. If you treat all people nice you will leave a good impression, and you never know when you might have to do some project, need help or a favor from this person sometime in the future. If you behave like a jerk they will remember that.

Also succeeding in the workplace is by being able to keep positive relations with people around you. The result of projects and work will be much better if the chemistry between people is good.

Smile
The flight attendants have special courses where they learn to always smile. They smile even if they have a crappy day. It is pleasant to see other people that smile. If everybody that is around you looks grumpy you will soon start to feel grumpy yourself.

Nobody really wants to deal with grumpy people. If you have a job where you can lock yourself in an office for a whole day it do not matter if you look grumpy, but as soon as anybody pops their head trough the door you should flash those teeth.

A smile will give off a sign that you are confident and friendly.