To turn on spell checking for all buffers:
:set spell spelllang=en_us
To turn on spell checking for only the local buffer:
:setlocal spell spelllang=en_us
Turn off spell checking:
:set nospell
When the cursor is on a mispelled word, use "z=" to see suggestions.
"]s" jump to the next mispelling
"[s" jump to previous mispelling
Add the word that the cursor is on to the internal word list:
zG