Ultimately, the most important thing needed is a large amount of respect for the capabilities of infants on the part of the caretaker. In order for a study to be facilitated successfully the caretaker must possess the belief that infants are active learners and explorers and are able to take risks and succeed with challenges.
It's also important that the caretaker be an active observer. Infants communicate their interests through their body movements, their sounds, and their eye gaze. In order to plan a study that will engage the infants the caretaker must be actively observing what items or phenomenon catch the attention of the little learners.
I think it's also necessary that the caretaker be able to take risks and think outside of the box. Infants are active learners and are eagerly soaking up information about the world around them. As such, it's not necessary to engage infants in play with highly commercial items. Some of the best investigations by infants and their caregivers involve everyday objects found around the home and school.
In order for a study to begin the willingness to continue to observe the infant's interactions with the materials and the ability to scaffold new experiences with the material as the littlest learners become more confident and competent with the material they are investigating is needed.
I can't stress how important I think it is to be an active observer. It's during those unstructured moments of play that the infant's curiosity is engaged and we are able to catch that curiosity and introduce new experiences.
As an example, here are some photos I took of the very beginning stages of a study of paper the 6 month old infant I care for and I are embarking on. And what sparked this investigation? The simple act of my ripping a page out of a magazine and the look of astonishment on his face and the reach of his hands towards the magazine.