Where do you place 'please' in a sentence to sound the most polite?

Solution 1:

"Please" at the beginning of the sentence places it in the position of imperative, which can make the please sound like a command. This usage is more direct, even though the imperative verb comes second. I think would one more often get a command from a computer or similar that says "Please insert..." than "Insert ... please".

At the end, "please" serves to soften an imperative.

But this is a minor distinction, and both ways are fine.

For maximum politeness we would say

"Could you please pass the milk?" or "Could you pass the milk please?" or "Please could you pass the milk?"