Question: What should I chant if I wish to pay respects before images of different Buddhas (e.g. Medicine Buddha) and Bodhisattvas (e.g. Ksitigarbha Bodhisattva)? I only know how to chant ‘Amituofo’ (Amitabha Buddha; 阿弥陀佛).
Answer: If you cannot differentiate or remember all the names, it is alright to always chant ‘(Namo) Amituofo’ (南无/阿弥陀佛), as this name represents all Buddhas and great Bodhisattvas too, as can be seen at http://purelanders.com/2013/04/22/amituofo-as-one-all-buddhas
Note that all great Bodhisattvas are manifested ancient Buddhas, while all Buddhas are one in terms of the Dharmakaya (Universal Body). ‘Namo’ means ‘homage to, and refuge for life in.’ Although chanting singularly, as long as in your mind, you are expressing utmost reverence to all Buddhas and Bodhisattva collectively, it is adequate. If you wish to chant homage specifically, here are some common formats:
Medicine Master Buddha: (Namo) Yaoshiliuliguang Rulai 南无药师琉璃光如来
Ksitigarbha Bodhisattva: (Namo) Dizhangwang Pusa 南无大愿地藏王菩萨
Guanshiyin Bodhisattva: (Namo) Guanshiyin Pusa 南无观世音菩萨
Amitabha Buddha: (Namo) Amituofo 南无阿弥陀佛