Missile infantry is very cool, it allows you to drown the enemy under a storm of arrows. Needless to say, it's not meant for close combat and we should avoid it whenever we can. I know there is missile infantry with decent melee skills, but they're usually expensive and unprofitable. The first game in which I've come across units that do both functions well is Three Kingdoms, but those units are still too expensive.
There are some points to keep in mind when using missile units.
- Firing to the front of units with big shields is a waste of ammo (not for guns).
- Shots to the rear do more damage than frontal ones. Surrounding the enemy with missile infantry and shooting from behind is as dangerous a maneuver as effective.
- If you fire at shielded units to the side they don't carry the shield, it's as if they didn't have them. Cool, isn't it?
- There's friendly fire. That is, if you shoot at enemy units that are fighting against yours, your soldiers will die too.
- How to make good use of ammunition is something you learn over time. At the end of the battle usually appear very good opportunities, try to reserve some ammo.
Bows are the most flexible from ranged weapons. Their weakest point is their low penetration power. Therefore, they are more useful against light or medium units. On the other hand, they are cheap and excellent for wiping out enemy units at distance. If you don't know what to choose, choose them.
In addition, arrows can be fired indirectly, into the sky. It is useful at certain times, but less effective. Ammunition is often wasted when used in this way.
Similar to bows; slings do less basic damage but more by penetration. Most important, they have more ammunition. Its optimal use is to stone the most powerful enemies from angles they cannot protect themselves with shields.
More penetration power than bows, but slower reload. Take advantage of it and use them against the most armored foes. Another point is that they can't use flaming shots, so if you intend to attack settlements be sure to take a couple of artillery pieces or archer units with you.
In addition, crossbows are the easiest way to finish off heavy cavalry and enemy generals thanks to their penetration power and, thanks to the fall of bolts and the size of cavalry, they can shoot safely from behind a spearmen unit.
Javelins and other throwing weapons
Javelins are excellent ranged weapons. Despite their short range and low ammunition, their high damage means that a unit of javelinmen can beat almost any other combat unit at range. Keep this in mind, whether you are using or facing them.
On the other hand, due to their low ammunition, it's very important to use them wisely. If you don't see the hole clearly, or there are friendly units between you and your foe, don't use them. Wait for the battle to advance and some breaches will appear. Another option is to surround the enemy and throw the javelins against his back. Javelinmen are the best on this role.
The best shots are the direct ones, but in order to make them you need to be able to draw a line between your unit and the target. That's why enemy soldiers who sneak into your lines are the perfect target. If your strategy is based on ranged dominance, leave gaps between your units, so that your ranged units can use them to shoot at the enemy. Playing as Partia there's a strategy that consists in having a line of persian hoplites in front of the archers, and when the enemy is ready to charge, activating the phalanx formation. As the soldiers tighten to enter in phalanx formation, gaps are opened between your ranks, by which enemy soldiers sneak in and are shoot down.
If the objective are big units: cavalry, elephants, giants... There's no need to leave gaps, due to their big size your missile units are able to shoot at them safely behind your spears. There are some units so massive that can cross your spear lines to crunch your missile infantry, beware of them.
Using the terrain
Direct shoot lines can be generated by taking advantage of the terrain. There was a guide that explained very well how to use imperial gunners, if I eventually find it I'll put a link. The esence was quite simple, put your units in a way that allows them to have a clean sight of the enemy. Here you have some examples of how to take advantage of the terrain with missile units.
The example above is thought for gunners, which are the most restrictive weapon. With another kind of weapon shots can be done with a smaller angle, due to the fall of the missile.
But the best one is always...
Observe the terrain before the battle, and if you have any ideas that you think can work, try them! Creativity is the essence, and my favorite part, of these games.