i can only say what i used to do. I dont know whether it will work for others. I used to break the quant section down into parts. I had practiced enough to get a sense of how much time i was spending on each ques so would only look at the time at the end of each 10 questions. I would b comfortable with say something like this:
if I was on the 11th ques then if there was 52-53 minutes left
on the 17th ques i would want to be on the 35 minutes to go mark
on the 25th ques i would b happy to be on the 18 minutes to go mark
on the 30th ques the 10 minutes to go mark
guess on a couple of ques after the 30th ques just to claw back the time, not wild guessing though.
34th ques i would look to get to the6 minute mark
then take it from there
i certainly blieve that the earlier questions do carry more weight than the later ones so would give about 25%more importance to them
on the verbal section i never had many problems finishing in time so dont think m too qualified to comment on that. All the best with ur test