For non-native English speakers
Is there anyone who has fully understood this grammar point? Can you use the articles without thinking, even though there's no such concept in your native language? If yes, then this question is for you:
HOW DID YOU DO IT?
Did you memorise all the Murphy's grammar books? Is it the result of reading fiction and/or watching films? Did you go to an English-speaking country and had an epiphany during the conversation with a bartender? Did you sell your soul to the devil? What did you do? Please tell me. I'm all ears. If you don't want to write it publicly, please (please!) send me a personal message.
For native English speakers (if you have read this far for some reason)
What do you think sounds less weird?
Q: What do you do?
a) I'm student.
b) I'm the student.
In case you're wondering: I'm trying to develop a strategy "when in doubt".
I have a friend in England who is from a Slavic-speaking country. She taught English in her home country for several years, has a Proficiency certificate and has lived here for many years with native speakers. At one point, she got fed up of making mistakes with articles so she asked her housemates to mercilessly correct every mistake with articles she made for one week solid. She is now better but not perfect.
I agree with everything Phil said. He recommended substituting "one" and "that/those" as a check. More extreme options would be "any" and "the only". So if you say "I'm the only student", the effect might be more obvious.
Another thing worth mentioning is that "a/an" and "the" are sometimes used for dramatic effect and, in such cases, non-natives will find it even harder to work out the rules in play. For example, I have a son called Tom (actually not his real name). I sometimes say things like: "You're being a lovely Tom today". I have characterised his name as a species, like "a cat", but just playfully.
In terms of sounding less weird, you mean that instead of saying 'I am a student' you say one of those other options?
I mean, they both sound bad. But 'I'm the student' is at least a grammatically correct construction in other contexts whereas 'I'm student' is not correct under any circumstances. So putting an article there is better than nothing I guess, although like I said it still sounds bad.