Okay, so if you have male anatomy, this post is not for you.
Men, stop reading now. This is one of those areas where ignorance is bliss.
When I was breastfeeding I had the lactation consultant's number on speed dial! I rarely pumped so it really did not matter what setting I had it on...until I went away for several days. So, I thought I'd post this for all of you who may be using the Medela Pump In Style Original breast pump. Because the numbers do matter!
To maximize volume start with the the Primer Rate. (Turn the dial to 4/5.) Once you've let down, reduce it to 1/2/3 (set the suction on the place that feels most like your child feeding).
I hope this helps!