This article addresses the special challenges associated with collecting longitudinal samples of the spontaneous sign language and spoken language production by young bimodal bilingual children. We discuss the methods used in our study of children in the United States and Brazil. Since one of our goals is to observe both sign language and speech, as well as any language mixing, it is important for us to address issues of language choice and techniques for directing the child participant toward primary use of the target language in each session. Suggestions and guidelines for achieving this in effective yet respectful ways are presented. We are especially dependent on the participation, flexibility, and direction of our participant children's parents, who work with us to elicit samples that are genuinely representative of their children's linguistic abilities. We illustrate our procedures for training parents and other interlocutors in data-collection sessions. In return for their generous participation in our research, we address parents' questions and concerns about language development, especially in bimodal bilingual contexts. We take very seriously the need to negotiate with participants regarding their expectations for the use of the data they provide, and we abide by their wishes in this matter. The strategies presented here improve the quality of the investigations we can conduct by making the experiences of the participant families as pleasant as possible.