Your motto is to always be prepared. So, for when Jeff and Lauren invite you onto their boat this winter, being prepared means showing that you do belong. This is the Emily Post-style guide to etiquette on a yacht, importantly including what not to do. “Be Prepared” and “Always Ready” Like the mottos of Scouting America and the U.S. Coast Guard, make this mantra your North Star. The boat has a skilled crew and top notch chef, so it’s going…