You can read endless customer management articles through Harvard Business Review. You can watch endless TED talks on motivation and how to motivate others. You can go to school for years to learn about sales techniques and buyer motivations.
But in the end nothing is better than simply being a straight shooter.
Tell it like it is. Keep the sentences simple. Tell your people when they seem to be swaying or falling off the tracks. Satisfy the buyer. Do what has to get done, then move on.
Don’t complicate things by holding opinions in, trying to add yet another case to the sale, weaving in complicated programming, or forcing those around you to say “I don’t understand, can you explain this again?” Complication breeds frustration. Holding in opinions breeds frustration. Not telling people what they really need to hear brings problems in the long run.
Keep things simple. Shoot straight to those around you. It’s best for all involved.