It's my first year living on my own (used to live with parent, and so she takes care of the lai see to everyone working for the building) so mom told me to prepare lai see (one packet only since i'm single) to security guards (i manage to remember their faces!) and the cleaning lady...
Other than that, I don't have to give lai see to any one at all...
As for the amount, lai see is just a little loaded gesture to greet others with luck during the CNY. $20 is a general amount, $50 to someone you think it's worth a bit more, $100 is almost from someone much senior, and i usually get $500 from my boss.
For couples, you give a pair to that someone only he/she knows both you and your spouse, give 1 otherwise.
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