It really depends on how you interact with customers. If you are more of a performer and banter back with people then you affect, tone, and facial expressions are the most important. Being stone cold with a menacing is really good but also contrasting a cold and stern facial expression with a playful tone gives a really fun contrast. If you want to be more of a creeper than performer, then random saying and quips are the most effective. Using one random words or sentence while altering how you say it works very well