When I open a set, after the opening dialogue runs out, I have a hard time transitioning into material that will keep the set alive. It could be my openers, maybe they're to closed-ended. Any advice on how to fix this?

transition stage is usually the toughest thing when first getting into game, you will find it will come naturally but until then here's some stuff:

This will only work with more than 1-sets:
"How do you guys know each other"
"Oh thats so cute you both have the same little nose wiggle when you laugh"
"Wow, how long have you two been fighting for the same guy" -if you've built some sexual tension
"You look like the good one, so that makes you the badass?"

you can always spin off if you have nothing to say and meet back with them later:
I.E. "well i gotta get back to my friends/work/living the good life, maybe ill see you around"

_________________
-dw3llz

Thanks a ton man. Basically I should just play off the group itself. I fell stupid cause that seems so simple. Once again thanks.

Don't feel stupid.
Most the stuff can be terribly simple once you get get in the flow of things.
In my opinion after i open a set i make a observation
If the girl isn't a 9 or 10 its a compliment then neg.
If she is a 9 10 i go right for the neg then DHV right after.