What is the right way to decline an offer?

I received two offers for similar positions. They were pretty equal, except in construction salary. One was about 30k higher than the other. When I decline construction employer A's offer, should I state it's because I have another offer from construction employer B for $XX? Or, should I keep it more generic and simply say the construction salary offered doesn't meet my requirements? Don't write a letter that could resurface in the future when/if you ever talk with this construction employer again about a job. All it would do is remind them that you rejected them. It's better to call the construction manager and explain that after careful consideration you have decided to do something else. If he presses you, don't divulge where you're going. I'd like to keep that confidential for now, but once I'm settled I'd like to get in touch to say hello and tell you more about what I'm doing. I was very impressed with your team.