6. Typing ":set xxx" sets the option "xxx". 

Some options are:

'ic' 'ignorecase'   ignore upper/lower case when searching

'is' 'incsearch'   show partial matches for a search phrase

'hls' 'hlsearch'   highlight all matching phrases

You can either use the long or the short option name.

7. Prepend "no" to switch an option off:  :set noic