No need to flatter, but you need to get along well. Treat him with respect. Show him respect. E.g. when we are alone and touching each other, I say by first name. When anyone's there, I touch, but I say boss. Don't use a word or a prefix at all. Always agree, but express rejections or doubts very diplomatically. He can be sent to the ass with a smile and nice words, so that he will still thank you. He must not negotiate with the boss, especially the vain. "Do what feeds you!" The boss writes salaries and rewards, even if it is cattle and is wrong. But he decides if I have butter and ham on the bread.