• :nohlsearch
  Use when you're done with looking at the last search. Specifically, it turns off the highlighting of the last search (just a temporary change — the next time you search, it'll be highlighted)
  
  
• :match, :2match, :3match
  Highlight a pattern, without affecting the search result. By using :match, :2match, and :3match, up to three can be active simultaneously.

  Use :hi to list all available {group} colors. Example call:

  :match ErrorMsg /foobar/
  :match Err^^ {group}

• matchadd()
  (requires Vim 7.1.040 or later) The lower-level version of :match that allows unlimited matches to be added.
  Example call:

  :call clearmatches()
  :call matchadd('Search', '^ERROR.*')
  :call matchadd('S^^ {group}
  

  " <leader>l = lock in the current-search pattern
  " <leader>L = clear all locked-in search patterns
  nnoremap <leader>l :call matchadd('Visual', @/)<cr>
  nnoremap <leader>L :call clearmatches()<cr>
  
  

• MultiSearch extension (improved version)
  An extension that allows you unlimited number of simultaneously active searches+highlights.

configuration settings

• wrapscan — whether the search wraps around to the top of the file after hitting the bottom
  (it's too bad Vim doesn't do the "intelligent wrapping" that things like Visual Studio do... i.e. wrap only ONCE, and STOP searching after you get back to the original point that you began searching at. i.e. never duplicate search results)