After the 1st PC, you're left with 4 pieces from a bag. Make a setup based on these 4 pieces.
2nd PC setups have an extremely high chance to PC. All but 2 patterns have a 90% or higher chance to PC. Knewjade wrote a guide that has 13 patterns which cover all 4-piece combinations left after PCO, as well as some that aren't possible with PCO. four.lol has a guide in English with the same patterns. It can be good to use patterns that have a slightly lower chance to PC but a way higher chance to save O for 3rd PC.