You're making this way more complicated than it has to be.
Next time you get a number, you wait a day or two, then the conversation should go like this:
You: Hey Sarah, Todd here, I just had the best time at [name some activity/event], thought i'd reach out and see how you were doing.
Sarah: Hi Todd, that sounds like fun, im doing good thanks for asking
You: That's really good to hear. What's your schedule like this week? We should get together for a drink.
Sarah: I'm free Thursday or Sunday night.
You: Ok, see you at Johnson's Pub Sunday at 8pm. Here's the address: ________
Anything other than the bolded (a direct answer stating her availability) is low interest and you should go no contact for another week or so, then re-attempt greeting her and asking her out one more time.
The most efficient way to sex is not trying to raise Sarah's interest level through small talk/idle conversation. Girls know how attracted to you they are right away -- so approach more girls and find ones that have higher interest level who will accept your date offer.