basic mac shortcuts

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cmd-a | select all
cmd-c | copy
cmd-v | paste
cmd-tab | shift between current and last used application
cmd-w | close current window
cmd-q | close current application
alt-right | move one word right
alt-left | move one word left

intermediate mac shortcuts

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---: | :---
ctrl-a | beginning of line (or fn-left for home)
ctrl-e | end of line (or fn-right for end)
ctrl-d | forward delete
ctrl-k | kill to end of line
ctrl-y | yank the killed text back (separate from copy paste clipboard)
ctrl-o | paragraph break but keep cursor is same place
ctrl-t | transpose letters
opt-delete | delete previous word
ctrl-b | move back one letter
ctrl-f | move forward one
ctrl-n | move next line
ctrl-p | move previous line
cmd-` | to shift to between the current and next windows within the same application
ctrl-cmd-shift-4 | select screen area to capture to image in clipboard (handy for pasting screenshots in an email)
ctrl-shift-power | (on macbook air) lock screen, if require password immediately is set for after sleep or screen saver begins
F1-F12 | in system preferences, keyboard; use all F1, F2, etc. keys as standard function keys (press the Fn key to use the special features printed on each key)
tab | in system preferences, keyboard shortcuts; enable full keyboard access (tab can move keyboard focus in all controls)

I like using a dvorak–layout keyboard as I touch–type; this can be set in system preferences — keyboard