This is what I did, and it worked incredibly well because it was honest:
Customer: "Hi, can you please give me your best price on a 2015 X-and-such with x,y,z options?"
Me: "I can. Are you using the bigger rebate for the special financing?"
Customer: (Assuming they know which incentive they're going to use) "I want the special financing."
Me: "Truly brilliant, Mr. Customer. Are you a member of the military? A recent college grad? A current (same brand) owner? A (competitive model owner?)
Customer: "No. Yes. No. No."
(The customer knows I'm looking for rebates, so my questions are therefore pertinent. They're also now getting accustomed to answering my pertinent questions)
Me: "Excellent, Mr. Customer. You're genuinely a member of the Coalition of the Ascendant. What trade in do you have, if any?"
Customer: "What does that have to do with it?"
Me: "Everything." (We all know this is true. I just had the audacity to say it...the customer doesn't know what to say to this)
---------------------------------------------------------------------------------------------------------------------------------------------------------------------Different paths
Customer: "I have a (year)(make)(model)."
Me: "Here's your price" (low-balled because I'll pinch)
or
Customer: "I'm not going to discuss whether I have a trade in at this time."
Me: "Great. Here's your price. (low-balled because I'll pinch from the trade...and yes, if a customer won't discuss a potential trade when asked, 9 out of 10 times, there's a trade. Customers who don't have a trade typically consider it safe to say so and just want price, like the internet tells them to do...those who do have a trade are often times told by the internet to not tell the dealer they have a trade. I've can't remember a time when a customer didn't have a trade and wouldn't say so)
or
Customer: "I don't have a trade in"
Me: "Lucky you. Here's your price" (price in the soup, that I'll honor if they come in)