"Fluff" topics largely depend on you & the specific girl. What are you interested in, what stories do you have, what are your aspirations, what do you find is fun. You also need to keep a grip on gratis dating to where you'd like the conversation to end up, and ways for you to demonstrate value, tell funny anecdotes, turn questions round to her and get on her a date.
Some good topics I find:
- travel stories, especially ones that are exciting, unusual or adventurous
- embarassing stories, usually involving drunkenness & misbehaviour
- real or imaginary stories about friends (you can use this to introduce / screen for the qualities you want, eg by recounting your "badboy" friend who has 6 girlfriends on the go, and watching her reaction)
- both of you people-watching, especially if there is someone gaming someone else. "Hey, see that guy? I bet he's going to offer to but that girl a drink. Look, he's leaning towards her, his body language sucks"
- talking about / screening for bisexuality "the barmaid is really cute" "have you ever been to Freedom on Wardour St?" "Oh, come on, that's such a cliche... ALL girls fancy Angelina Jolie, pick someone more original"
- music (especially if your tastes are similar)
- good places to eat / drink
- psychology (leads into doing the Cube, or similar)
- foreigners & accents..... "if ah waz French, an ah spoke eeen a French accennnnt, then ah would prrrrobably already 'ave my 'and on your knee, like zis"