QUOTE
when naruto was fighting to sasuke, he had one-tail out,
Confusion, betrayal, helplessness, anger, desperation
QUOTE
when naruto was training and met orochimaru at the bridge (after rescuing gaara) he had four-tail out,
Again, betrayal, helplessness, anger, desperation, especially after Kabuto taunts him with words that hits these spots right on
QUOTE
when hinata was hit by pein he had six-tail out (hix)
Shock, grief, pain, sense of loss, loneliness, anger, futility, especially after all the carnage of Konoha that he just learned since he came back
My interpretation is that Naruto is more likely to release tails when he is
emotionally hurt to a great degree. Basically, the more negative, inward emotions he feels, the more likely he won't be able to keep his tails in check. Another way to put it is that the more emo-angry he becomes, the more tails he grows. There's also the obvious interpretation that the more times you've been in tailed mode, the easier releasing tails becomes.
Naruto fought Gaara when he was younger, more naive, with less fear, and that fight he was preoccupied with two purposes: to protect Sakura from death, and to show Gaara the light. And both were possible and he was determined to make them happen. It wasn't a situation that would cause Naruto to go emo since there is still the little bit of hope. Add in the fact that Naruto has only borrowed bits of Kyuubi chakra before and has never released any tails at the moment, it's not surprising that no tails came out, because there were no triggers and he lacked the tailed experience. Naruto was at his best on that day, and when Naruto is at his best, you don't expect him to grow tails, do you? No, you'd expect him to fight like the Yondaime.