Maybe do a section on recommended cameras according to budget?

Have 30 second skits acting out your dos and dont's. Possibly in a Goofus and Gallant format.
If the viewers start to get bored, incorporating fake blood, severed limbs, and exploding organs will pep them right up.

I've skimmed through some of the horror-story threads, but most of what I've found in terms of photographers were stories of neckbeards grabbing candid upskirt shots.

Captcha: mylesti moral

Some stuff off the top of my head:

~ don't invade the privacy of others if it looks like they need it
~ asking is a must, but it's kinda okay to jump in when they're already posing for other photographers
~ if you believe the person is underage and they're doing poses you think of as inappropriate, it's better you walk away than look like a pervert (although you may need to consider this for people not underage too)
~ always try to tell people where you'll be uploading them to or where they can find them, you earn more friends and respect than some nobody who takes a snap and walks off
~ it's okay to ask if a cosplayer can do another pose or straighten one up so it'll look better in the end, most cosplayers are appreciative of being directed a little if it means a nicer photo

Thanks for the suggestions so far, guys! Much appreciated.

Cosplayers want to see their pictures. Make and give out business cards with the URL of your gallery so they can find them.

Take tons of pictures, but only upload a few. If you have six shots of the same exact pose, choose which one is the best and just upload that one. Don't be EBK, in other words. And as a courtesy to the subject, don't upload unflattering pictures unless it's something you can photoshop out.

Speaking of photoshop, nearly all pictures could use at least a little. Don't go overboard, but some minor light and color adjustments can make a big difference.

That's all I can think of from a cosplayer's viewpoint. And as obvious as it SHOULD be, please emphasize how completely disgusting and inappropriate it is to try and get panty shots without explicit verbal permission from your subject. Don't be that guy; we all hate that guy.

Photog here. Hm. What could you pack into a convention panel. Let's see...

Show people good photos. Explain why they are good. Show bad photos. Explain why they are bad.

Explain some stuff that people should keep in their head like headroom (I see a lot of photos where the subject has this big blank spot above them for no good reason), where to frame (ie. don't crop people's limbs off at awkward spots), and in general basic composition. Tell them not to use a wide angle lens close up because of the distortion and show them the difference between a wide angle shot and a telephoto shot.

Tell people to move people to less cluttered areas. You know what really annoys me? Random shit in the background. Move them towards a wall or off to the side. Yeah, this might not always be feasible (especially with dealer hall photos) but a lot of cosplayers are willing to work with you.

Poses. Good pose/bad pose.

Show what lighting can do. Show what the pop-up flash does and why you generally don't want to use it, what an external flash can do (plus bounce flash), what off-camera lighting can do, etc. Add some stuff about natural light.

Someone mentioned recommended cameras. I'd go as far as to say recommended cheap gear. For example, instead of buying a first party flash which can cost a ton you have alternatives like Yongnuo, Metz, Nissin, and others (even if it is arguable that you might save money with first party flashes because they're pretty damn good). Lighting on the cheap like flash umbrellas, cheapo Chinese reflectors, etc. Lens recommendations. Canon's 50mm 1.8, Nikon's 35mm 1.8 and 50mm 1.8, etc.

Oh and tell people to resize their photos. A really shitty photo at 100% can become a half decent one at 25%. At least you see less of its shittiness.

That's all I can think of off the top of my head. I'm going to sleep now but I'll be checking this thread in the morning.