I have a previous answer on the subject of archer recruitment and background in English forces of the Hundred Years War. Unfortunately, we do not have an enormous deal of evidence about specific archers and their careers. There are no sources that would help us to understand what trained looked like specifically for future military archers. Some evidence (such as later Tudor accounts, the famous laws mandating Sunday archery practice, court cases about injuries resulting from archery practice) does indicate that archery was a widespread social activity in medieval England, but the soldiers who participated in the Hundred Years War were often from a relatively narrow demographic: the middling classes of society, such as tradesmen and moderately prosperous farmers. They were often from families that had a high number of veterans to begin with. So a young man in such a military family might well do more practice than the average English villager of the time. It is also likely that he would practice other skills, such as riding or swordsmanship, along with older brothers, fathers, or uncles who had previously served. The same families often contributed both archers and men-at-arms, which means that a new archer recruit might well have experience sparring with an armored opponent. The lack of documentary evidence means that we do not have much evidence for how young an archer might be. There is at least one skeleton of an archer from the Battle of Towton who was 16 at his time of death. Anne Curry has traced the career of Robert Fishlake through his deposition in a court case and came to the conclusion that he was around 16 when he began his military career. So there is evidence available to show that a military career might begin at a fairly young age, but I wouldn't take that conclusion too broadly.

The usual range for English longbows is pegged somewhere around 250 yards (there are arguments for slightly lower and slightly higher figures). I could go on about equipment, but /u/waritter already produced a rather definitive summary of the typical arms and equipment for English archers and men-at-arms during the Hundred Years War.

Any specific era in history? Archers have been around a long time.