Use the proper article:
a) One morning ... little boy is sitting in ... bus on his way to ... school. He's sniffing all ... time and making such ... noise with his nose that... other people in ... bus begin to shake their heads. At last ... gentleman who's sitting next to him says: "... little boy, haven't you got ... handkerchief?" "Yes, I've got ... clean handkerchief in my pocket," says ... little boy, "but I can't let you have it. My mother says it's not polite to ask anybody for ... handkerchief. You must use your own."
b) ... Englishman and ... American were taking their dinner at one table without being introduced to one another. During ... meal... American asked ... Englishman to pass him ... salt. "Here's ... waiter, sir", replied sternly v. Englishman. "Oh, I beg your pardon, I was mistaken," said ... American. "What? You were mistaken, sir, you took me for ... waiter?" "Oh, no", answered ... American. "I considered you ... gentleman".
c) Waitress: ... coffee, ... orange juice, ... egg sandwich and ... cheese sandwich. You: Thank you. ... coffee and ... egg sandwich are for me, ... orange juice and ... cheese sandwich are for my friend.
d) Teacher. Are these your things, Peter? ... pen, ... English dictionary, ... notebook, ... camera and ... bag. Peter: ... camera and ... bag are mine, but not ... pen, ... dictionary, or ... notebook.