Using pure vi commands:
Copy to a named buffers, e.g. r two lines of text
Insert the contents of buffer r into current cursos position.
Search a text forward
/[text_to_search] and backward
Repeat the search forward press
n, and backward
Search and replace, i.e. substitue general command:
:%s/the/The/g 	 Replace the with The. % means the complete file.
:%s/the/The/gc 	 Replace the with The but ask before substituting.
Repeats the last action press
.(dot) key in edit mode
Execute a command from within vi do
For instance, change file permission to allow you to write without close it
:!chmod +w %. The
% will be replaced by the file name.