If you want to centre, or right or left justify your text, chances are you will reach over to your mouse and head for these icons at the top, right?
Well, this is a very laborious way of doing it - why use the mouse at all, just learn the shortcuts!
CTRL+E to CENTRE JUSTIFY
CTRL+L to LEFT JUSTIFY
CTRL+R to RIGHT JUSTIFY
The first one isn't maybe so logical, but you will soon learn it. The second two are easy to remember. The only strange thing is that because L is to the RIGHT of R on a QWERTY keyboard, and if you're like me, you will sometimes confuse the two! But then I can never remember which is left and which is right when I am crossing the road, so that is hardly a good indicator...