Sayyidah Aishah (may Allah be pleased with her) narrates that the Prophet (peace and blessings be upon him) loved to begin with the right in his ablution, when he (peace and blessings be upon him) performed ablution, and when he (peace and blessings be upon him) combed his hair or when he put on his sandals as well (he preferred the right side).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 403