Pumping for 24 hours - Tips please

Courts

I am going to be away from my baby for just over 24 hours when she is 5 months old. She is exclusively breastfed. I have pumped before, but not since she was a newborn. I will need to leave enough milk with her dad to cover the time i am away. What is the best way to pump this milk before i go? How much will i need and when should i pump so i dont mess up my supply. I have about a month before i go, so plenty of time.