you said "some" did you narrow your choice down yet. i have a rule never date anyone you work with.
reason why is if you get into a relationship and it doesnt workout. the person who got hurt can spread horrible rumors about the other person in the office, creating a uncomfortable enviroment.

to approach someone i think you have to do it without thought. strike up a conversation about something simple like the weather.
the person your interested in do you know if they are single, or thats something you have to find out?