Some airlines allow parents with young kids to be the first ones to board a plane. A smarter move is to be the absolute last passengers on board. The goal here is to minimize the amount of time a squirmy, curious, potentially ill-tempered infant is stuck in a confined space. Rather than preboard, run kids around the airport to tire them out. Just before boarding, visit the terminal bathroom, which will have way more space than the plane's for changing diapers and helping older kids use the facilities.