bare with me
I'll be keeping my clothes on, thank you very much
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Talking about armor and swords is good and all. Just make damn sure you can also talk about the historical context of the arms and armor. If you're going to present a knight in the 1250's, be prepared to talk about the events of the 1250's.
There's a lot of work that goes into researching and learning a particular era or topic.
1. Become familiar with the topic or era. Keep it specific. Don't try to learn all about the Middle Ages, keep it to something small like the Norman Conquest or the First Crusade. That being said, it is imperative that you know the surrounding context of a historical event.
2. When you've identified the topic or era of most interest to you, read up on the historiography of that subject. It's boring, it's dry, but it's necessary. You need to know how other historians have studied, what the different interpretations are, who the current historians are, etc.
3. Go out and read books. Make sure the book is published by an academic press and by an author with a PhD in the subject. Make sure the book has footnotes and a works cited section. Also, make sure the book was published recently. History doesn't change, but how it's interpreted does. Books by journalists and popular presses are generally sh**. They are not held to the same degree of quality and credibility that academic books are.
4. Read scholarly articles on the topic. Scholarly articles are published in quarterly academic journals and are peer-reviewed. Random internet articles can't be trusted. These can be found on Google Scholar, JSTOR, or Project Muse. If you have a library card, you should have access to these.
5. Now that you have an idea of modern interpretations, you can start digging into primary sources. Use the footnotes and works cited sections of books to identify primary sources. Search around for databases of manuscripts and artifacts.
6. Now you can go talk about it.
As for an accurate kit, make sure you are close enough that it is recognizable. On the other hand, you need to be able to identify what is wrong with your kit and why. A good kit should be backed by primary source evidence. It should most certainly be constructed of period materials. Hand-stitching for visible seams is preferred. The items incorporated should also be appropriate for your impression. Don't wear something because it looks cool, or because it was "period correct". The most period correct gear is often times the gear you make yourself (depending on your skill) or custom made gear. Take Ian for example. He couldn't find shoes that were correctly manufactured, so he made his own. He needed a new arming garment, so he sewed his own. If you've got the skills to do it yourself (and make it look nice), you'll save money and have more accurate custom gear.
As far as re-enacting etiquette goes, be mature and respectful first and foremost. If you want to be more professional, keep quiet and observe how others act, then adjust your behavior in accordance. Leave the joking and pop-culture references at home. Clean up your spelling, syntax, and grammar (that goes a loooong way).
In the end, like everything else it takes experience. The more you do it, the more adept you will become.