The factors that most often influence a person to learn to speak another language fluently are:
1) speaking more than one language at home, work, or school, 2) having a native language full of foreign words, 3) living in a country influenced by other cultures, 4) living in a country with open borders next to countries speaking another language, 5) have a love for learning languages, 6) have exceptional memorization skills or 6) have extreme attention to detail and enjoy grammar.