A good battle to research for answering your question would be the Battle of Fontenoy, which was a French victory in 1745 over the forces of the "Pragmatic Allies", English Dutch and Hanoverian.

The two sides were evenly matched in numbers. It was a very bloody and close run battle. It was a combined arms battle, with infantry, cavalry and artillery all playing their part.

The allies were attacking. The French defending (defending their siege lines around the fortress of Tournai).

The battle opened with an allied artillery bombardment at long range of the French lines. The allies then attacked both flanks but were repelled by French artillery and infantry. The British and Hanoverian Infantry then made a great advance in the center, accompanied by their guns.

They pushed through French flanking artillery fire, came over a small crest, and face to face with the French guard.

This led to an amazing battlefield conversation, which seems entirely representative of 18th century warfare.

With the lines of musketeers face to face at close range, Lord Charles Hay of the British Guards, saluted the French and said, "Gentlemen of the French Guards, Fire!". The Comte d'Auteroche replied, "Gentlemen, we never fire first. Fire yourselves!"

In any event, the French did fire first, but their volley was not particularly effective. The British then commenced rolling volleys and drove the French backwards.

All looked lost for the French. Louis XV's advisers were urging him to flee, but Maurice de Saxe, general of the French army, said. "we must all conquer or die together", and threw his cavalry against the advancing Allies.

The cavalry forced the Allied infantry to form square. This allowed them to shatter the French cavalry charges, but made them more vulnerable to the French cannon, which continued to pour in fire from the flanks.

As the Allies fought off the French cavalry, and began to advance again, Saxe threw in his artillery reserve, four guns loaded with grapeshot, and six battalions of Irish "Wild Geese", fighting for the French.

Grapeshot and the Irish reserves stopped the Allied advance, and the Allied troops somehow managed a disciplined and fighting retreat.

The Allied Cavalry, which had been underused so far, charged to good effect to allow the infantry to re-organize and retreat in good order.

Casualties were high on both sides, but the Allies retreated and the French held their ground, allowing them to claim victory, and later complete their siege and capture Tournai.

Artillery was used in the whole battle. The guns were used both from fixed positions on the French flanks, and as mobile field pieces, advancing with the Allied assault, or racing into position to try to stop it.

The main aim of the artillery was to shatter infantry or cavalry formations. Infantry was particularly vulnerable to artillery when formed in square (usually to protect itself against cavalry). If artillery could have broken the squares, cavalry might have poured through and slaughtered the infantry.

Even though the Allied infantry were forced into square by the French cavalry assault, the cannon fire on the squares, though devastating, did not manage to break them.

In this battle, each side had about 50,000 troops and about 100 guns.

The main difference between artillery in the Battle of Fontenoy, and artillery later in the Napoleonic Wars, was that most of the guns at Fontenoy were 3 pound, 4 pound and 6 pound guns. By the time of the Napoleonic wars, field guns were at least 6 pound, or, more frequently 12 pound guns.

This was made possible by a redesign of cannon in the 1760s which allowed 12 pound guns to be made weighing almost half as much as they had previously weighed, which allowed them to be used as field pieces.

6 pound guns (or smaller) were very marginal in having the power to shatter infantry formations (as confirmed much later by the US army in the Mexican American War). 12 Pound guns were much more effective, but at the time of 1745, were too heavy be mobile on the battlefield.

Artillery was used in a couple of ways - as a physical weapon, but also as a psychological tool at unnerving the opponent. Can you imagine marching into cannon fire, not knowing if your line was to be targeted, seeing rows of soldiers being taken out with just one hit?

Initial bombardments - yep. The closer the enemy ventured, the more precise the artillerymen would become. Upon really close range, grape-shot would be used to take down masses of infantry. There would usually be sustained artillery fire throughout a battle, yes.

A very effective tool in any battle, and still is today. You can imagine, back then, that armies marched in strict line formation, making a huge target out of themselves.

Napoleon himself was an artillery officer before rising to prominence.