It's easier to train a smart person than an idiot . Hire smart people. Hire happy people. You earn it by being better than the rest. Don't tell them what to do, show them what to do.
Role play .
Present real world situations and let two members of the team take opposite sides of the fence. Teach them how to help and how to give value . Don't just teach selling skills. Teach buying motives. People don't like to be sold, but they love to buy.