How should Truthful Speech Be?

The Lord has said in the Geetha:
“Anudhvega karam vaakyam sathyam priya hitham cha yath”
(Speech that does not offend, that is truthful, pleasant and beneficial, has to be practised).
Such speech sanctifies the tongue.

Related excerpts from discourses
1. Sathyam Brooyath
Even when speaking the truth, one should not inflame passion, diminish enthusiasm or inflict injury:
“Sathyam brooyaath, priyam brooyaath” (Speak the truth, speak pleasantly).
“Na brooyath sathyam apriyam” (If unpleasant, do not speak the Truth).
“Priyam cha na anritham brooyaath” (though it may be pleasant, do not speak falsehood).

2. Sathyam Brooyath
Manu gave to the world yet another profound declaration:
“Sathyam brooyaath, Priyam brooyaath. Na brooyaath sathyam-apriyam”
(Utter the Truth. Say what is pleasing. Never tell what is truthful but unpleasant).
This means that you should not speak an untruth because it may be pleasing to one. Nor should you speak out the truth when it is likely to hurt a person’s feelings. Every man should speak the truth, but it should be truth that is pleasing.
In the Gita it has been stated:
“Anudvegakaram vaakyam Sathyam Priyahitham cha yath”
(In speech, the words should not cause any excitement, they should be true, pleasing and well-meaning).
When you see a blind man, you know that he is blind. This is true. But because it is true, if you hail him as: “Oh blind man!,” you will be causing him pain. As soon as he hears the word “blind,” he feels distressed. No doubt what was said was true, but it distressed the hearer. Likewise, on seeing a lame man, if you accost him as “Oh lame man,” you will be causing him pain. In the name of truth, one should not utter words which cause pain to others.