Let us say that you are about to put a caller on hold, what will be the most appropriate thing to say? You need to ask if it is okay that you put a caller on hold. If the person answers yes, then say thank you. If the person answers no, then you have to explain why you need to put the caller on hold.
There are two possible reasons for this: the first reason is you have call waiting and there is someone calling on the other line. The other possible reason is you are going to retrieve the information that the caller needs. You would like to know if you want the caller to be put on hold or if the caller prefers that he/she would be called back.