When Sarah meets Adam in the dinner she orders a milkshake. In one shot she is seen taking the straw cover off, then in the next few shots it is back on. Finally when Adam leaves the straw cover is again off.
When Sarah and Mark start to make out on the park bench their heads are tilted to the left of each other. Then, in the reverse shot their heads are tilted to the right. And then, back and forth again.