In the world of sword-arts, HEMA (Historical European Martial Arts) occupies a unique place as it is, by and large, an amateur pursuit. “Amateur” here is not a put-down, just the appropriate word to use, because apart from the few accredited fencing maestri out there who represent living traditions and work on the older stuff, most everyone else comes to HEMA as an interested enthusiast. Many if not most of us started in sport or classical fencing or other martial arts (e.g. Asian martial arts), but unless you’re young and a more recent student of historical fencing, chances are good that you learned from someone who has just been working on something longer than you have. That is okay, it’s just how it is, but not all instructors are equal and it pays to do your homework.
This is an important consideration as there are increasingly more people setting themselves up as instructors and without a viable certification program how is one to know if they’re worth visiting? While in time some qualification process might be in place, and as nice as a certification program might be, it would still be wise to have some guidelines for judging potential teachers as even some qualified instructors, no matter the field of study, can be stinkers.  One needs to have some measure by which to evaluate them as well as a handy list of red-flags.
The following check-list is a place to start—you may have individual concerns to add to the basic list. However, if a person or school fails most of this list, I’d recommend you keep looking:
School/Group Culture: The general feel of a place can tell you a lot about the person or people running a school. How open and friendly are they? When you call, email, or visit them, how quick are they to respond and how openly? How inclusive is the school—are there women there, younger students, older students, people in different states of fitness? What is the school’s focus? Does it tend toward the scholarly (source-driven, play oriented); is it purely tourney centered, is it a mix?
A lot comes down to what you want. If your interest is to fight in tourneys, then you should look for a school that does that and an instructor who has that as one goal for their program. There’s no wrong answer in terms of what you want—some people just want to fight, some people want to build a more complete skill set and understanding regardless of tourneys, and still others want the SCA without all the rules. Find the culture that appeals to you. This said, any version of these schools is probably going to be a better fit if they’re friendly and open to a diversity of students.
Personality: Tied to culture, the instructor’s personality has a lot to do with a school’s culture—people gravitate to people they relate to. Whatever an instructor’s focus within HEMA there are some things to look for and not surprisingly they’re tied pretty closely to the same openness, friendliness, and sense of community mentioned above. Is the instructor arrogant? Do they build students up or tear them down? Do they praise and encourage when making corrections or embarrass students? How do they respond to questions? You’re spending time and money, and unless being abused is your thing it’s probably best to keep looking.
Experience/Qualifications: This is one of the hardest things to assess and because of the diversity of sources, not to mention instructor experience, it will vary. A lot. This said, there are again some general guidelines. Some instructors may know a lot, but be poor teachers; others may be good fighters, but know little of the source material; still others might be a decent mix of both. Many think they know a lot or have a lot of skill, but are really little more than attribute fencers with deep ego needs. If you can find a healthy balance of knowledge and skill, great, but you may need to compromise and that is okay. It may take a few visits to see what sort of person you’re working with too.
If you have no previous background in fencing or related arts, it can be extremely difficult to judge an instructor’s knowledge and skill. But there are some tells—any instructor who has spent serious time studying martial arts will have a degree of humility and will acknowledge the skill of his or her peers. Generally, they are cautious and tentative in presenting new material—all HEMA is interpretation and some interpretations are better than others. Anyone telling you “no, this is how they did it” without decent evidence is someone to avoid. Likewise avoid anyone pretending to have learned something in secret–more often than not this is going to be pure bull-shido.
If you find someone who is at constant pains to brag while putting down their peers, that’s not a good sign. A good instructor will be able to explain where something comes from, say a particular move, why we do it, and how. They’re open to questions and different points of view. They should be able to point to the sources they use too. A good instructor will also admit when they don’t know something; even better instructors will then help you find an answer. A good instructor will push you to improve, but will be supportive and encouraging in doing so. This stuff is hard enough without some jerk making you feel bad about it.
Approach: Since we’re talking HEMA, there should be a fairly large emphasis on the H and the MA side of the acronym. Ostensibly any instructor in HEMA is looking at the sources—if not, I’m not really sure what they’re doing.
We know the little we know and we build our interpretations of past combat arts from surviving sources.
The martial arts aspect is important too—the goal should be “don’t get hit” followed by “hit and don’t be hit.” If either of these is missing, you’re in the wrong place.
Remuneration: Different schools and instructors have different rates. Comparative shopping is important. Most schools struggle to stay open, so what you pay generally goes to rent and gear. Few people make a living teaching historical fencing.
Look at their pay structure against what they teach. Do they have options for payment? HEMA is expensive, make no mistake, and many instructors will work with you to find a way to make dues less onerous. Floor fees are common, but many schools will also give you a first visit or two free. That can be a good indication of what to expect. If someone offers individual lessons, ask them how they run their lessons, what they generally teach, and how much they ask.
Safety: Better instructors will have a culture of safety and enforce it; they will seek to prevent injury, not encourage it. There’s a fair amount of macho, HEMA-bro-culture out there, sadly, so if you’re into that nonsense, go for it. It won’t be hard to find. It seems silly to have to list this, but given the general machismo when it comes to safety it needs to be said: find someplace safe. Does your instructor require the basic safety equipment? Do you see people fencing without it? How well do they take care of the masks, gloves, jackets, etc.? How courteous are fencers with one another? How courteous is the instructor? Are they using insufficient equipment for the weapons they train, and if so, do they have protocols for how to do that safely?  Do they have insurance? Have you signed a waiver?
Everyone wants to get fighting as quickly as possible, but jumping in, full bore, on the first day is not wise. Learning how to fight with swords takes time, drill, patience, and dedication—you don’t make progress over night, but over years. Be wary of any program ready to throw you into the mix with no to very little training. The truth is that any fencing school must consider the lowest common denominator when it comes to safety, not the best case scenario.
In summary, here are the basic red-flags. If you see any of these, walk. Your time, money, and safety are worth more.
- poor ability to take criticism or correction
- narrow-minded, bigoted, or predatory
- lack of qualifications (this includes appeals to secret knowledge or training or connections to dubious “experts”)
- incapable of or unwilling to work with others
- incapable of or unwilling to appreciate student ability/gifts/credentials/questions
- problem child in larger community
- dangerous and unconcerned with safety
- discomfort with students visiting other schools or instructors; cultish possessiveness
To be honest, sometimes you can’t see all the red flags right away, especially if you’re an occasional visitor and/or if the problem instructor is good at hiding it, but it will out. The community, wherever you are, generally has a decent notion of where not to go.
All of this assumes you want to learn swordplay in earnest and well. It’s a long, difficult path to proficiency, and you have to be willing to put in the time. Find an instructor who can not only impart technique and passion for this complex field of study, but also one who will be there to help you and keep you going when you’re ready to quit. Any such instructor is, by definition, not going to have a lot of these foibles.
 The HEMA Alliance has such a program, but not everyone in HEMA is part of the alliance and their program is not universally accepted. See https://www.hemaalliance.com/instructor-certification
[update 10-4-19: There are some organizations I forgot about and share here. One is AIMA (Associazione Italiana Maestri d’Arme) and the other is one branch of the sport org AIMS (Associazione Italiana Maestri di Scherma), which has certified a number of Maesti di Scherma Storica (historical fencing).
 There’s a difference between “this is how we interpret this passage” and “because I say so.” Context is everything, and some sources are much more difficult to work with, and thus, force us to be more tentative.
 Most clubs use normal fencing masks. They’re the most available, most affordable option, but they’re not designed for anything heavier than epee most of the time. So, if your interest is longsword, overly heavy sabre (i.e. trooper weight meant for use in the saddle), pole-arms, etc., be sure to ask how the school mixes these weapons with fencing masks. It can be done more safely, but any mask can fail. One of my favorite examples of just how easily a fencing mask can be crunched is here: https://www.youtube.com/watch?v=eW1Imv7yHig