Here are just a few tips I’ve learned that make the interactions between a cosplayer and a non-cosplayer much more pleasant.
If you want to take a picture of or with the cosplayer, you should probably ask first. There are really only two scenarios that I can think of where not asking first isn’t such a huge deal: if you’re taking a video while walking through the convention or if the cosplayer has amassed a horde of people and everyone else is taking a picture. The former usually ends up in a video on youtube and the latter is often seen with group cosplays. But, as a general rule, if you’re not sure, just ask. However, it is possible the cosplayer may say no. For the love of all things that are holy, don’t get offended. They may be tired and trying to get out of their costume, maybe they need to meet someone, or are going to a photo shoot. Overall, they are not intending to be rude so don’t be rude to them. Speaking of rude things, taking a picture of someone without their permission is pretty rude. Don’t do it (how many times do I have to reiterate this?).
Don’t hog the attention of the cosplayer. If there’s other people who are waiting to take a photo with the cosplayer, you’re only inconveniencing them if you start up a conversation with the cosplayer. If you feel you really need to talk to this amazing cosplayer about their costume or the media their costume is from, exchange numbers or instagrams. You can talk later. Another bad time to start up a conversation is when the cosplayer is walking somewhere with a purpose (you know, THAT walk). As mentioned earlier, they probably need to be somewhere else at the moment and you stopping them to trade a bit of banter is probably not helping.
DO NOT TOUCH. Do not touch a cosplayer, their costume, or their props without permission. You don’t know how breakable their costume is; do you really want to destroy someone’s hard work because you wanted a hug or wanted to touch their prop? You also don’t know if the cosplayer is even comfortable with a complete stranger touching them. As always, the golden rule is: ask first.
(A weird one, but…) No tipping required. Normally, when you see a cosplayer out on the convention floor, you don’t have to pay for a photo (yes, I’ve been asked if I take tips…). There are some cosplayers, who work for companies, that do take money in exchange for photos. But, they’re normally at a booth, not shuffling through the convention hallways.
If they’re relaxing, don’t bother them. Specifically, don’t ask for a photo (unless they have all their gear on already). But, if they’re relaxing, they’re probably more likely to say no to the photo (I know I would). If they’re in armor and have taken off a few pieces, it inconveniences them to have to get up and throw everything back on to take a single picture and then turn around and take it all back off again. However, it’s totally fine to go up and talk with them.
There are probably a few other general rules I’m forgetting, but if you follow the above guide-lines, I think you’ll be alright.