I Got 1 1/2 Oz!!!

That's GREAT!!!!

It is totally normal for the milk to stop after a little while. If you keep pumping, it will start back up (that is your second let-down). I always had to pump through at least two letdowns in order to increase my supply. Sometimes that would take me the better part of an hour (I know, I was obsessed with it, but with our difficulties, it was necessary if DD was going to get any breastmilk at all).

some tips that helped me:
try to relax.
take deep belly breaths like you learn in childbirth class.
visualize milk squirting out with each exhale.
think of your milk filling baby's tummy.
you really have to love your pump in order to give it milk - our bodies just aren't designed to feed a plastic machine.
adjust the speed and suction settings on your pump to closely mimic the way your baby nurses. For me this was a faster speed and softer suction. Keep adjusting the speed and suction until you know what works for you. sometimes it helps to either speed up or increase suction after letdown starts.

Congrats!!!! I have a really, really low supply so I think 1.5 oz is fantastic!

Pumping gets easier with time. As you get used to it, you probably won't have to jump through as many hoops to get that much milk.

It helps me to have a pic of my babe nearby, and to think of him while I pump.

I also second the recommendation to wait until your second let-down. The let-down reflex is tiny muscles in the milk ducts relaxing and letting the milk flow. I guess they eventually contract again, and if you keep pumping they will relax again. My guess is that this is what signals the body on whether to keep producing the same amount or to prepare to produce more.

Also, I don't know if you asked this, but it's normal to get different amounts from each breast, and for the milk on one side to stop flowing earlier than the other side. At least, it is normal for me.