As a Chinese student myself, I find it's a common problem among a lot of my fellow students even some of my teachers, (and me of course) to make such mistakes, like saying "he" while actually refering to "she" and vice versa, in most cases, unconsciously. Yes, we don't even know about it when we are speaking. But as listeners, we can easily tell that someone has made the obvious mistake. Have you experienced such a situation？ and how would you feel？
Of course I have heard this mistake, as it is quite common.
I am mindful to offer an explanation when the person is finished speaking.
However, I will not bother with pointing out the mistake, if I understand generally,
what the person is trying to say. If, for example, we are discussing something very important, I would never both offering a correction because when something very important is being discussed, there just is no need or time for trying to correct petty mistakes in grammar.
There is a time and place for correcting petty mistakes in grammar.
Usually, I will just make a mental note and at some future time I will explain the gender distinction.
Hehehe. Actually, as a native speaker of American English, it is a little funny to hear someone say "she" when they are actually talking about a guy. It is like you are saying he is like a woman. Not that there is anything wrong with being a woman, but some guys might get offended and have their pride hurt. Hehehehe.
Sometimes I correct someone when I hear it but sometimes I don't. It depends. I feel like I am being rude if I correct someone sometimes. It is even worse though if someone says "it" instead of "he" or "she", because then it is like you are saying they aren't even human. A lot of people would be sooooo mad if they overheard you refer to them as "it" when speaking about them to someone else. Hehehehe
Thankfully, English doesn't have grammatical gender like Kovichenko mentioned about Spanish, but English still does have gender specific nouns like "waiter" versus "waitress". It would be really funny to hear someone call a guy a "waitress" actually. Hehehehe
I think the mistake that English learners make the most though is when to use "the" or "a / an" and when not to use either of them at all. I don't know of any technique you could use to prevent yourself from making these mistakes though. Sorry. :/
I think for me this is not an issue. Being Spanish my native language, we also have this grammar rule. And it even goes beyond... we need to remember the gender of every noun! haha. For example chair is female, car is male... English native speakers have a hard time learning all this.
I would say it's something you just need to remember, like I must remember the tones in Mandarin, even though I don't have to in any other language.
I think when you learn a new language you need to not only add vocabulary into your brain, but also change the way it works, otherwise people might understand you, but it won't be natural.
For this particular grammar point, maybe a trick could be... imagine he is a short for the male/boy, and she is an abbreviation of the female/girl.
It's actually a pretty funny mistake to make sometimes. Especially if you're talking about both a guy and a girl and you mix them up. I have a buddy from Mexico who used to always mix them up and as a result there were a few times that he said some pretty amusing things.
I always commit gender grammar related when it comes to spanish.. Even if I know the rule it is just that I forgot to use it or maybe I didn't noticed that I neglect it maybe because I am in a hurry or too focus to say what I have to say lol.. Well speaking while thinking those grammar rules and remembering the vocabulary makes me lag. >< Anyways those kind of mistakes will be minimize as the days goes by especially when you always speak the language you are learning.