The goal in any melee is to concentrate a lot of your firepower on a small area of the enemy's formation without allowing him to do the same to you. Assuming that both sides start with equal numbers the only way to do this is to force some of the enemy to waste their time while their teammates are eliminated. To achieve that we use formations, tactics and strategies.
Time is very critical to the success of any mass actions. No matter how clever your plan, if you give the enemy enough time he will find a way out of it. Therefore, when you execute a plan you should do so swiftly, hitting the enemy while he is still surprised.
In a match up of 2 on 1 the 2 should almost always win, no matter the skill of the 1. However, for that to be true the 2 must attack boldly, simultaneously and without pause, or the engagement may become 2 sets of 1 on 1, where the more skilled fighter is more likely to win.
Given equal numbers, the advantage of attacking an enemy on two fronts seems to outweigh the disadvantage of splitting up your forces. That means it is usually a better idea to split your forces and come at the enemy from two sides at once.
If your forces are in disarray or are flanked, a quick retreat and regroup is usually better than standing your ground. Standing your ground generally allows your forces to be mopped up piecemeal.
Groups that work together generally do better. Very skilled fighters have an unfortunate tendency to split up and work as individuals rather than as a team. A team of less skilled opponents who work together can often defeat them by using team tactics rather than counting on individual skill.
Any time a fighter finds himself with nothing to do during a melee, that probably means the enemy is flanking his team or concentrating their firepower in one area. The team commander should look for those idle fighters and quickly assess where the enemy went and where they are concentrating. He should then move the team to where the maximum number of his people are engaged with the enemy. Any idle fighters should expect and be ready to be moved at any time or should take the initiative to look around and quickly fill in where they are needed.
Every fighter should be very careful not to throw blows too hard in melee. Instead, plan on striking each target 2 or 3 times. Fighters are often too excited to notice hand shots, so avoid throwing them. Also, taking a hand or arm still leaves the fighter able to fight. Hitting the leg, body or head will take a fighter out with one hit.
Hand shots are a mixed bag. On the one hand, hands and arms are the most accessible targets, especially in a static line fight. Learn to hit those arms as the enemy throws shots at you, rather than exposing yourself to go for his hand when it is at rest. On the other hand, taking a hand or arm still leaves the enemy able to fight, whereas a head, body or leg effectively ends his ability to melee.
Fighters who become angry or too excited in melee will lose their ability to function effectively. Every few moments take a deep breath and re-focus.
A fighter who falters while his team is engaging the enemy can take the initiative away from his team. Each fighter must trust in the team's plan and boldly execute their part of the plan -- including engaging the enemy -- without hesitation.
Every fighter should always have something in their off hand. If the fighter is new and has no skill with secondaries, he should at least carry a 17" to 18" buckler, which will provide some protection just by being held in front of the fighter.
I have found that a 40" epee and as large a shield as is allowed is an effective combination for a skilled fighter. Experienced fighters tend to shun bucklers and other shields in favor of more offensive weapons but I believe that is a mistake. A shield is a very effective defense against multiple opponents and can ward against multiple attacks at the same time. That is important because as a skilled fighter AND a person with a 40" blade, you will almost certainly be targeted for quick elimination by 2 or 3 opponents. In addition, shields can block attacks that you do not even see coming, freeing a bit more of your attention to concentrate on killing with that long blade. Daggers, by contrast, only defend against attacks you see coming and dagger kills in melee are very, very rare.
A commander needs to walk a narrow line between leaving his troops without direction and giving trying to direct too much of the details. You only have one set of eyes and will not be able to see everything at once. Give your troops enough autonomy to get their jobs done and smart, capable people will find ways you never thought of to reach their goals. This is especially true when doing strategic planning before the beginning of the battle. Give your sub commanders a good idea of the overall plan and then give each sub commander a mission. Properly worded, those missions should require minimal input from you after the battle has started and the flexibility to adapt to changing conditions.