I do a lot of my anime watching in public spaces - on the subway, at the gym, anywhere where I need to kill some time or distract myself. I'm not alone - I've spotted plenty of other anime fans in the wild, doing the exact same thing.
While there's nothing wrong with indulging in your media of choice in public, there are ways to do it way, way wrong. In the interest of not being public nuisances, lets go over some of the Do's and Don'ts of public anime consumption.
~Know something about the series in advance. This is not the time to be using the random button on Crunchyroll. If you're watching in public, there is a nonzero chance that someone else will see the contents of your screen. As such, you need to have some level of control of what appears on said screen - and you can't have that if you don't know episode 6 is going to spend five minutes talking about boners and episode 7 is largely dedicated to murder.
~Pay attention to your surroundings. You may be watching anime on the subway to avoid human interaction on your commute, and that's cool - but you don't want somebody walking off with your wallet, and you don't want to miss your stop.
~Be aware of your data plan! You don't want to be slammed with a huge bill because you streamed three episodes of The Ancient Magus' Bride on LTE. Unless you have unlimited data or are totally cool with wasting money, try to find a public space with free Wi-Fi. (Public libraries are amazing for this.)
~Watch ecchi, harem anime, hentai, or anything else that's sexually explicit in public.
Here's a confession - I actually kind of like A Sister Is All You Need. It's typical siscon grossness, but I find the characters oddly compelling. Yes, I'm fully aware that that sounds like the otaku version of reading Playboy for the articles...and that's exactly why I don't watch it in public. Because Ms. Random McRandomson sitting next to me on the D train doesn't know I'm not actually a sicko, and she didn't ask to see animated, nipple-less titties during her commute. Neither did the seven-year-old sitting on the other side of me. Rule of thumb, if you wouldn't tell your mom about a series, don't watch it in public.
~On the same note, save the super violent stuff for the privacy of your home. Recently, I made the mistake of trying to watch an episode of Berserk at the gym. I ended up stopping the episode almost instantly because there was a demon whose body was made of intestines. The dude on the treadmill next to mine was a little scared of me after that - but hey, if you want to repel dudes at the gym, maybe do watch Berserk in public?.
~Watch without headphones, or watch with your headphones turned all the way up. Literally no one except you wants to hear what you're watching, so respect the folks around you and keep it down.
~Ignore the rules of a public facility. I once saw a guy sitting in a coffee shop watching Naruto two minutes before the shop was supposed to close. If a coffee shop is closing in two minutes, you should be leaving, not getting your nerd on.
If you stick to these simple etiquette rules, you'll have a great public anime viewing experience. If you have any other hot tips, or want to fight me about whether or not it's okay to watch hentai in public, leave a comment!