The infantry have always been the basis for any army and at the time of Waterloo, this was certainly the case. Unlike cavalry troopers or artillerymen, an infantry soldier could be drafted in with very little training. The term 'cannon fodder' is often used to describe the basic foot soldier of the time; such was the low regard in which he was held by generals. Soldiers who distinguished themselves as being of higher than average quality, in terms if accuracy of shot or fitness, were generally picked out to join the elite units; grenadiers or light infantry. After a sufficient period of service, a soldier may be given the honour of joining a guard unit. In Napoleon's army, a soldier had to have 12 years' service to be eligible to join the Old Guard.
An attacking infantry unit would very rarely fire at all
Infantry were armed with a long smoothbore musket, fired by a lump of flint striking against a serrated steel face. This was accompanied by a socket bayonet which would be attached to the muzzle for close combat. Guidelines varied between the armies but there were anything up to 20 separate steps involved in loading and firing a musket. In the heat of battle, an average infantryman could reasonably be expected to fire one or two shots per minute. Since the effective range was about 60 yards and anything further than 100 yards was completely safe from harm, this did not afford a great deal of opportunity for the extended fire fights so popular in films. More reasonably, an infantry unit would fire at most two volleys and then prepare to accept a charge with bayonets. An attacking infantry unit would very rarely fire at all.