Ctrl Shift C to copy, Ctrl Shift V to paste (use Cmd instead of Ctrl if you're on a Mac). Best done in grid view.
However, you should be working like this - Auto Sync mode. In Develop, Ctrl/Cmd click the Sync button which switches you to AutoSync mode and from now on your adjustments will apply to all images currently selected. It's much faster than the copy and paste two step.
John