Lick somebody’s boots
Definition 1 of 1
Pro Tip 1/3Negative Connotation
The phrase often implies desperation or subservience, and is usually viewed negatively. 
As soon as the supervisor walked in, Mark started to lick his boots, losing respect.
Pro Tip 2/3Metaphorical Use
It's used metaphorically to describe overly flattering behavior, not literal boot-licking. 
Sarah didn't actually lick her boss's boots; she just compliments him excessively.
Pro Tip 3/3Informal Speech
Commonly used in informal situations among friends or in casual conversation. 
He's licking the teacher's boots to get a good grade, which everyone finds annoying.