To search, use the / command and enter a regular expression in the command line at the bottom of the window. This command is also available by the standard ⌘F key.
If the ignorecase option is set, case is ignored. If the smartcase option is also set, case is ignored only if the search pattern does not include any uppercase characters.
To search backwards, use ?.
To quickly search for the word under the caret, use *. The # command searches backwards instead.
You can repeat the last seach command in the same direction with the n command. The upper case N command reverses the direction.