Originally Posted by
BearX220
You go through immigration at Newark, show your passport and "enter the United States." Then you reclaim your checked baggage and take it through customs. After clearing customs you re-check your bag onward to SFO (there is a re-check desk right there, beyond the barrier) then proceed into the domestic terminal and locate the gate for your onward flight. Hopefully your schedule allows for at least three hours to accomplish this.
One thing to add here s that after you recheck your luggage and proceed to the domestic terminal, you will once again have to go through the domestic security checkpoint, wherein you must remove shoes, remove laptop from your bag (not your tablet, though), and go through a body scanner.