Most groups I've seen have no organization.
Having been in the military I always end up feeling like court martialling the lot of them after most battles...
I'm slowly starting to have an impact with my current group. But they still all want to be chiefs. I've just finally gotten them to be willing to carry ranged weapons and to try shooting a bit before the enemy fully closes.
However real tactics are still a long ways off.
If you're DMing consider trying clever use of a tower shield, spearman, and bowman. In a narrow hallway it's a deadly combination that will wreak havoc on the PCs trying to break through it.
Also try to engage the enemy at a crossways where you can come at them from multiple sides yet still box them in.
A four way intersection in a dungeon works great for this if you can get men on the sides.
Most PCs are stupid enough to choose the intersection to fight in. A good deal of the rest can be chased into it.
Especially if they're in "Everybody wants to be a star" mode... which 90% of the time players are; having seen way to many action hero movies...
Always keep a few men as far back as you can with bows or crossbows. If they've got feats make precise shot a priority so they can shoot into melees.
My archer PCs usually fights from 40 or more feet behind the rest of the party. Even the fool mages close in more than I do...
If there's no idiot to keep the enemy away from me I fight by shooting and falling back untill or unless I can get a defensable position.
When we're breaking into a facility and we're going through a door I always stand with a shot readied on anything that moves at a daignail axis from the door so that I can see into it as it opens.
If you're planning a dungeon give the NPCs means to raise an alarm. Consider giving them bells, gongs or whatever at any key guard posts. Signal whistles are great too.
Once the alarm is sounded you can pull that intersection routine mentioned above at every intersection for the rest of the dungeon...
Remember to dogpile. Have as many people as possible go after one target until that target is neutralized. Then move to the next target. Players may feel it's unfair when you use it on them. But NPCs should fight to win not to be fair.
Lastly once you do get some good tactics going remember to scale them for the NPCs. NPCs who are not seasoned combatants will not use all of your tactics. They should fight like players do...
I tend to have the 'greens' attack the PCs by order of PC charisma. They go after not the logical targets and not in effective ways. Rather they go after who they have a natural inclination to dislike the most. So the lowest Cha people take the most hits when they fight unseasoned opponants.