Looking on the internet deeply has found these results:

make an appointment is the most popular phrase on the web.

make the appointment 15,290,000 results on the web	make an appointment 185,200,000 results on the web More popular!
Some examples and use cases from the internet:	Some examples and use cases from the internet:
Sorry, I can't make the appointment tonight, I'm with a friend. If the matter to be dealt with is urgent, the chairman may make the appointment on his own initiative. But she'd have phoned the station to make the appointment? If you feel the same way tomorrow, ma'am... I'll even let you make the appointment. Charles: No, just You make the appointment, I'll take care of the rest. I'm so sorry I didn't make the appointment. Just make the appointment, Mr. Johnson.	Well, have him calm my office and make an appointment. You'll have to make an appointment at the mill office. OK, if you'd like to call back and make an appointment. I'd like to make an appointment with Dr. Wagner, please. You'd have to call me, make an appointment. I need to make an appointment with dean Reuther right away. You're saying I need to make an appointment.

make the appointment

15,290,000 results on the web

make an appointment

185,200,000 results on the web

More popular!

Sorry, I can't make the appointment tonight, I'm with a friend.
If the matter to be dealt with is urgent, the chairman may make the appointment on his own initiative.
But she'd have phoned the station to make the appointment?
If you feel the same way tomorrow, ma'am... I'll even let you make the appointment.
Charles: No, just
You make the appointment, I'll take care of the rest.
I'm so sorry I didn't make the appointment.
Just make the appointment, Mr. Johnson.