Smiling and nodding.

Doc asks patient: "So why the hell did you go outside?" (It was freezing and snowing and the old patient fell down and broke his leg)
Patient: "I wanted to see if it was slippery."

Patient answers the question why he came to the walk-in clinic:
"I'm freezing and I didn't freeze yesterday even though it was colder!"

Patient: "I have a headache."
(Geez.. Take two aspirins, go to bed, sleep a little, call your doc on monday..)

And the patients who are really sick, normally walk in, take a seat patiently, wait for 3 hours and feel very uncomfortable about stealing the precious time of the staff.