Actually, at any point during the test, remember that you should have 2 mins per question remaining for the leftover Quant questions and 1.5 - 2 mins per question remaining for the leftover Verbal questions.
Say, in Quant section, if time remaining is 60 mins, 15 minutes have elapsed so you should be around Q 7-8 (or further ahead). If time remaining is 30 mins, 45 minutes have elapsed so you should be around Q 23.... or say if 30 mins are remaining, not more than 15 questions should be remaining etc...
For Verbal, if 30 mins are remaining, not more than 17-18 questions should be remaining etc
But do not focus too much on the ticking clock... It will distract you and make you waste your time. Check that you are on track every 5 or 10 questions, depending on your comfort...