Without asking any questions or talking too much, I like to give the horse a hands on once over, taking my time. I may ask how he is about picking up his feet and then may pick one up. I may stand back and circle and ask a few more questions then I'll throw the whammy. I'll look at the seller and ask if the horse is on medication. The response can be the deal breaker. A heavily doped up horse will offer no resistance when you lift his tail by placing your hand under it near the anus. He should clamp it tight. Private sellers can be unscrupulous as well. So if told the horse is just relaxed it's definitely time to leave.