It is an incredibly huge and complicated topic, but this is a good summary: http://www.philosophybasics.com/movements_scholasticism.html

Basically:

• It should be seen as the foundation of everything we consider today academic and intellectual - a systematization of everything people knew or thought they know about science, philosophy, law and theology. It was its systematic nature that differentiated it from previous scholars who just basically investigated this or that independently, and created a systemathic synthesis of everything so that people can build on each others work instead of working in isolation. Given that this - the ability to build on each others work, due to systematization - is the very basis of what we today consider academic intellectualism, it is very hard to say why was it succesful. Academia is academia. You can live without it, but if you don't want to, this is how it started. Anything else could have been succesful, but would not have been academic. Even history itself.

• You could track it back to Anselm, but the most iconic momentAquina's reconciliation of Christian theology with Aristotle's philosophy, with a large chunk of influence from Arabs like Avicenna who preserved much of the Greek tradition. But, much broader, as a systematization of Greek philosophy, Roman law etc. reconciled with Christian theology.

• There have been competing schools in what to teach, such at theological differences between Duns Scotus and Aquinas. I am not aware of any competing ideas in how to teach.

• Educationally, it was based on dialectical reasoning. A heavy emphasis on logic. Experience played a role, it was not outspokenly anti-empirical, but given that neither the mathemathical methods nor the measurement devices existed for empirical science in the modern sense, deductive logic played a more important role.

• It was largely replaced by humanism, so that was its later, succesful competition. Basically you can see Scholasticism as a rigorous and kind of elitist, very academic attitude. Humanists like Erasmus challenged this elitism, to be blunt here: they wanted to be less intellectual and more digestible, practical and closer to the people. Worths quoting in full:

" Nauert (3) argues that the Humanists attacked the philosophical and analytical methods of Scholasticism, the dependence on Aristotelian philosophy and use of dialectic, because the humanists were concerned with moral rather than metaphysical certainties, and with rhetoric to explain truth, rather than dialectic which, in their view, spread confusion."

http://www.theologian.org.uk/churchhistory/scholastics.html

You can see something very similar to the Reformation here: more focus on morality, rhetoric, faith, and less focus on deductive, logical, metaphysical (i.e. geometry-like) reasoning. This is much similar to Luther's "faith must trample underfood reason". Or later in France the Jansenist-Jesuit debate.

Also: http://www.loc.gov/exhibits/vatican/humanism.html

Generally you could say that humanism in the educational context, and a something that was defined more or less against scholasticism and replaced it, focused on the human concern, the human interest, which means that classical works were studied more because it helped citizens learn to speak, write, debate, express themselves clearly, a more pragmatic focus, while Scholastics wanted to understand the deepest truths of the universe. So it was less academic and more pragmatic.

The Scholastic would focus on training specialists, lawyers, doctors, theologicans, the Humanist would focus on training well-rounded citizens who can think, speak, research etc. in whatever work they choose to do.

The Scholastic would prefer with Aristotle the vita contemplativa over the via activa so the life of a detached, obsering intellectual, the Humanist would prefer an active life.

This is surprisingly good for wiki, the summary: http://en.wikipedia.org/wiki/Renaissance_humanism

Renaissance Humanism is often said to have "rediscovered" the classics. Iti s not true, much of the classics, Aristotle etc. were already in use long since. What RH did is 1) focus on the less scholarly and more literature type classical works, poetry etc. 2) not studying it as a detached science but as a pragmatic tool to life, to learn how to speak well wetc. hence the term humanism or humanitas, it did not simply mean less focus on the supernatural but mostly it meant a focus on a active life, being a politician etc. (Machiavelli) and not a scholar-monk who observes life but does not participate in it.

In different countries, universities, different departments, actually traces of both are alive today. Scholasticism is the specialist training, and the view of the detached, theoretical scholar, Humanism is those universities who like well-rounded students to do sports and volunteer or something, not just learn science or philosophy, and generally they expect students to take what they learned into "real" life, private sector jobs, journalism, social activity, politics etc. etc. and not just into academic jobs.

This is also very good: http://books.google.com/books?id=9vdgJRASHtMC&lpg=PP1&pg=PA3&redir_esc=y#v=onepage&q&f=false page 3-4 cannot copy-paste from it but essentially it explains well: Scholastic: be a scientist, Humanism: be a leader.