People often complete tasks and to-dos not only for themselves but also for others in their household. In this work, we examine how household members share and accomplish errands both individually and together. We conducted a three-week diary study with eight households to understand the types of errands that family members and roommates share with each other. We explore their motivations for offering and requesting help to complete their errands and the variety of methods for doing so. Our findings reveal when participants sometimes face challenges completing their errands, and how household members request and receive help. We learned that the cooperative performance of errands is typically dependent on household members' location, availability, and capability. Using these findings, we discuss design opportunities for cooperative errands sharing systems that can assist households.