I have a 100% close rate on candidates we've given an offer to (so far). My one trick is that I'm honest about downsides and am looking out for the candidate's interests. That's it.
You might not be able to figure out exactly what they're hiding, but it's obvious they're lying to you and will say anything to close the sale. When most people do that, honesty stands out!
Non-commission dealerships like CarMax have been wiping the floor with dealerships that employ stereotypically slimy salespeople.