Respect and communication is the key. I've seen two cuddlers in the past few months but I've seen one of them several times. Even though I know her boundaries, I always ask "Is this ok?". I told her to be blunt and even elbow me if needed but she never has! But seriously either ask before you try something new or try it and ask if it's ok.
Boundaries should be discussed, by the pro, prior to your session beginning. It is good to have a conversation so you both know what to expect. There are several prompts I give to discuss boundaries, beginning with my CC profile. I am always willing to discuss what my cuddlers want. If a person is creepy, after the boundaries are set... I bounce.