Advice from multiple stakeholders is required to design the optimal pediatric clinical trial. We present recommendations for acquiring advice from trial experts and patients/caregivers, derived from advice meetings that were performed through a collaboration of the Collaborative Network for European Clinical Trials for Children (c4c) and the European Patient-CEntric ClinicAl TRial PLatforms (EU-PEARL). Three advice meetings were performed: (1) an advice meeting for clinical and methodology experts, (2) an advice meeting for patients/caregivers, and (3) a combined meeting with both experts and patients/caregivers. Trial experts were recruited from c4c database. Patients/caregivers were recruited through a patient organization. Participants were asked to provide input on a trial protocol, including endpoints, outcomes, and the assessment schedule. Ten experts, 10 patients, and 13 caregivers participated. The advice meetings resulted in modification of eligibility criteria and outcome measures. We have provided recommendations for the most effective meeting type per protocol topic. Topics with limited options for patient input were most efficiently discussed in expert advice meetings. Other topics benefit from patient/caregiver input, either through a combined meeting with experts or a patients/caregivers-only advice meeting. Some topics, such as endpoints and outcome measures, are suitable for all meeting types. Combined sessions profit from synergy between experts and patients/caregivers, balancing input on protocol scientific feasibility and acceptability. Both experts and patients/caregivers provided critical input on the presented protocol. The combined meeting was the most effective methodology for most protocol topics. The presented methodology can be used effectively to acquire expert and patient feedback.