Cmd-J - New layer via copy
M, B, J, and S keys to switch to the marquee, brush, healing tools, and clone stamp
Cmd-D to deselect
Cmd/Alt-delete to fill with the foreground and background colors
Shift-delete-bring up the fill dialog
Cmd-T free transform then shift-option drag to constrain proportions and transform from the center
Shift-Return - Highlight the numerical adjustment in the toolbar or properties panel
0-9 keys change the opacity of a layer or brush opacity