Copy and paste styles between layers in QGIS

If you have one layer nicely styled and then you want to style another layer in the same way in QGIS, you can do it by copying/pasting the style from one layer to another. So long as the layers are both of the same type (e.g. both polygons) and you have similar data in them (e.g. the same value that you've categorized or colored them by) then you're all set!

It can save you many clicks.