i - insert before the cursor
I - insert at the beginning of the line
a - insert (append) after the cursor
A - insert (append) at the end of the line
o - append (open) a new line below the current line
O - append (open) a new line above the current line
ea - insert (append) at the end of the word
Ctrl + h - delete the character before the cursor during insert mode
Ctrl + w - delete word before the cursor during insert mode
Ctrl + j - begin new line during insert mode
Ctrl + t - indent (move right) line one shiftwidth during insert mode
Ctrl + d - de-indent (move left) line one shiftwidth during insert mode
Ctrl + n - insert (auto-complete) next match before the cursor during insert mode
Ctrl + p - insert (auto-complete) previous match before the cursor during insert mode
Ctrl + rx - insert the contents of register x
Esc - exit insert mode