Most folks I know use the Center tool in the Paragraph group on the Home tab of their Ribbon to center their paragraph. While this is quick and easy enough, I am one of those people who do not like to move my hands from the keyboard to the mouse to accomplish this. I just find it quicker and more efficient to just use my keyboard to accomplish this.
So, if you are like me and would to center a paragraph using your keyboard, triple click your paragraph and simply click Ctrl + E. The paragraph in which the cursor is located will now be centered.
I hope you find this shortcut helpful as well!