Sanguines are the social butterflies - they can become very trivial and socially shallow - but they can also use this social gift to great ends. Sanguine is the natural temperament of childhood - the happy, skipping little boy or girl merrily singing to himself is the picture of the sanguine stage of childhood (soon to slide into the more melancholically influenced stage of youth from 14 to 21). Sanguines can be real scatterbrains and one has to (gently!) help them stay focused (just as one has to help the cholerics - gently - lighten up a bit!!). In a classroom, the sanguines are the ones who are usually asked to run errands - "Tom, can you go get me some more chalk from the office" "Elizabeth can you please go see if our visitor has arrived " and so on. They finish their work very quickly and are ready for something new. There is a great art involved in balancing out this tendency to lightly travel through life so that it doesn't become facile or create an overstimulated personality. Moving through material fairly quickly but then ensuring one keeps coming back again and again to revisit and pick up on left themes is helpful. And giving them teaks to do is also helpful.
Melancholics are the classic "the glass is always half empty" kinds of people. They are heavy and often preoccupied with physical complaints - the child who always has a hurt, who is always talking about this or that complaint - usually in a sighing "woe is me" kind of way. Thy can become self absorbed but they can also bring their depth of perception to their work and be incredibly meticulous and methodical. Whereas the choleric can often turn out fabulous work by sheer strength of will (and no study) the melancholic will work and work and produce something marvelous. The phlegmatic can also set himself huge tasks and come up with the goods - but will go just so far - the melancholic, once he is engaged will be limitless in his studies.
Melancholics can be tricky - if you tend toward the choleric or sanguine, melancholics can be exasperating. Worse still, if you (like me) have a strong melancholic streak yourself, then they can really pull you down and you find yourself on the couch with them commiserating over the latest tragedy in life.... and never get on to what you were meant to do! Melancholics can be hard to inspire - in Waldorf classrooms, they are often put together so as to eventually disgust themselves into action. They are also often left to sit in the shadows, where they prefer to watch from the sidelines and from where, when they are ready, they will emerge. In many ways cholerics, even the ones who seem to have arrived at birth with their own agendas, can be easier than melancholics because the trick is to challenge them - and they will almost always rise to a challenge. But melancholics need to come at things from their own desires and can't be tricked, coaxed, challenged or harangued. Once they relate to the material, though, they will usually start to work - and once they are engaged, they are never shallow.
Phlegmatics are the solid ones - sometimes literally in their builds. They hang on. They can seem to be slow and are often very good natured - they are not fickle like sanguines or restless like cholerics or self obsessed like melancholics. They placidly regard the world and slowly decide what they are interested in. They will listen to any story - but getting something out of them can be a challenge. I have a strongly phlegmatic boy in the present sophomore class where I teach - he will literally count the words of the papers he writes and write not one more than required. So usually when he says "how long should the paper be" I say to him "As long as it needs to be to say what you need to say." He doesn't like that - but unlike a choleric who will be outraged by the seeming ambiguity of this requirement or the sanguine who will forget halfway what she was writing about anyway or the melancholic who will write exactly what she thinks is the right length no matter what the teacher says anyway, this typical phlegmatic just shrugs, smiles - and produces a very short paper!
So phlegmatics can seem to be hard to inspire and get going - and you can't really just leave them like melancholics as they won't usually come up with some brilliant work which originates in their ruminations. They will just sit there. Just keep plugging away and do not be afraid to experiment with phlegmatics - they rarely balk at sameness because they are happy for the predictability to lull them to sleep - they need to be gently jiggled awake by radical changes every once in a while!
You can look at the characters in Winnie the Pooh to find the four temperaments - Eeyore is the melancholic; Rabbit choleric; Pooh phlegmatic; and Christopher Robin himself is the sanguine (Piglet could be sanguine but worries too much. Roo is a pretty good sanguine).