The first was the Carolingian renaissance, begun by Charlemagne in the 8th century. He had most of the ancient books that have come down to us copied in newly-invented italic (lower case) script and preserved in monasteries. Charlemagne was also responsible for reviving Cathedral Schools in which children could learn to read.
http://en.wikipedia.org/wiki/Cathedral_school These taught the liberal arts and eventually became universities. During this period (commonly known as the Middle Ages) books and learning were the province of the clergy.
The Renaissance of the twelfth century was spurred on by the importation of books by Aristotle preserved by the Arabs, particularly his Ethics, which was a prelude to his Politics. During this period, as towns and trades flourished, there was a continuing need for lawyers and a demand for ancient texts about law. Chancellors of towns employed copyists who copied books for secular purposes. There was also revival of vernacular poetry at this time, particularly in Italy and Southern France. This was the time of the great cathedrals.
One scholar (Vossler) thinks the Renaissance began with Dante, about 1300. Dante's Inferno is modeled on Aristotle's Ethics. His teacher (Brunetto Latini) was a Chancellor of Florence. But most other scholars date the beginning of the Italian Renaissance to the Italian poet Petrarch, who belonged to the generation directly after Dante.
In !300 book hunting began in earnest. Petrarch and his circle discovered and had copies made of important books by Cicero (teacher of eloquence to lawyers) and Livy (a Roman historian). Petrarch called for a reform of Latin (then the language of learning) and Italian style. He also complained that Medieval books were hard to read and recommended a clearer handwriting (based on Carolingian) and less cluttered looking books. In contrast to the highly technical language of the Medieval philosophers, logicians, and theologians, Petrarch and his friends wanted to establish a clear way of writing that everyone could understand, on subjects that would help people live virtuously (as opposed to counting how many angels could fit on the head of a pin, say).
Petrarch was the first one to refer to the Middle Ages as a time of decline and he tried to learn Greek. And for Italy this was a time of humiliating decline. The black plague occurred c. 1347. During the whole century, the Papal Court had relocated to France. Petrarch's successors, the Italian umanisti, flourished in the 1400s -- the Italian Renaissance proper. By then the Papacy had moved back to Rome, and the Popes set out on a massive rebuilding project, taking antiquity as their model, as did other Italian cities. Even before the invention of printing many many more books were being copied and read by laymen (albeit wealthy ones) than in all the previous centuries. (Though the biggest libraries were owned by Prelates). Printing, discovered c. 1450 (?), begins on a massive scale in the 1500s. By the time the humanist movement got to Germany, France, and England, it had assumed a religious cast. English and French poets imitated Petrarch and his friend Boccaccio.
That is my highly simplified explanation of the Renaissance! Yes, trade, particularly banking (with interest) and double entry book-keeping were mightily important in stimulating the rise of the towns.