For the most part I like just having fun and joking around with people. I enjoy the light-hearted conversation with people and it helps make everyones day a little happier.
The seriousness of it depends on the situation. I've been known to "flirt" (joke around and banter) with older men (talking 70-90's here) while their wife's are saying "oh you should say __." That is mostly to make everyone smile, have a good time, and helps get through a day of customer service. Then there are my guy friends, who i've known forever and feel like "one of the guys" I'm just giving everyone a hard time, making jokes, making witty remarks, and what i just see as 'hanging out with the guys'. This one gets me into the most amount of trouble because often intentions are misunderstood (going both ways) and makes things uncomfortable for a while. When it comes to someone I have feelings for, however, I normally make a fool of myself every time I say something, so I just dont.
Overall I think how people react to flirting depends on their personality. It is important to realize someone might get the wrong intent behind your actions and you must be able to handle/deal with that situation gracefully, kindly, and gently when it happens.
Just my thoughts