The only advice I can give you is to take someone along with you; so they see you are incapable of taking care of yourself; that you need someone to help you think and speak, etc.
Y'see, if you come by yourself they already see you as competent enough. And seriously if they see any competence you lose your chances.
Then, do not respond to their questions sensibly. Honestly, if you do, they will say you are capable of holding down a job. So just answer stupidly. if they ask what is one plus one say eleven. Seriously. been there done that.
I'm sorry they make it so tuff for those who truly need it and a one-time appt. will not tell them much.
They do give weight to your doc's documentations. So hopefully your doc knows how to write up something convincing.
Not trying to cheat the system here, but the system is not very good at picking up when we truly need their help, so gotta work with what we have.
I was denied twice and then with the help of an attorney I got one year of disability. Still better than nothing. No one who knows me thought I could hold down a job at that time. The folks at work said I am so young yet have the energy of an eighty-year old. Would come home from work and fall asleep, could not take care of kids. Getting the benefits helped me take a year of from work and take care of my kids instead. And if there are no kids involved, you need to take care of yourself; you're also a person who needs caretaking.