By putting double quotes around a set of words, you are telling Twible to consider the exact words in that exact order without any change.
Attaching a minus sign immediately before a word indicates that you do not want pages that contain this word to appear in your results. The minus sign should appear immediately before the word and should be preceded with a space.
Attaching a plus sign immediately before a word indicates that pages must contain this word to appear in your results. The plus sign should appear immediately before the word and should be preceded with a space.
Typing the merchant's website address preceded by "site:" will return all results for that specific merchant. For example typing "site:www.comet.co.uk" will show all the voucher codes and deals for Comet.