George Bernard Shaw: Making

Preface
1910s, The Doctor's Dilemma (1911)
Variant: A life spent making mistakes is not only more honorable but more useful than a life spent doing nothing.
Context: Attention and activity lead to mistakes as well as to successes; but a life spent in making mistakes is not only more honorable but more useful than a life spent doing nothing.

Credited to Shaw in the lead in to the mockumentary C.S.A.: The Confederate States of America (2004) and other recent works, but this or slight variants of it are also sometimes attributed to W. C. Fields, Charlie Chaplin, and Oscar Wilde. It might possibly be derived from Shaw's statement in John Bull's Other Island (1907): "My way of joking is to tell the truth. It's the funniest joke in the world."
Another possibility is that it is derived from Shaw's characteristic of Mark Twain: "He has to put things in such a way as to make people who would otherwise hang him believe he is joking."
Variants:
If you are going to tell people the truth, you'd better make them laugh. Otherwise, they'll kill you.
If you're going to tell people the truth, you'd better make them laugh. Otherwise, they'll kill you.
Disputed

Variant: If you cannot get rid of the family skeleton, you may as well make it dance.
Source: Immaturity

Vivie, Act II
Source: 1890s, Mrs. Warren's Profession (1893)

H. W. Shaw (Josh Billings), as quoted in Scientific American, Vol. 31 (1874), p. 121, and in dictionaries of quotations such as Excellent Quotations for Home and School (1890) by Julia B. Hoitt, p. 117 https://archive.org/stream/excellentquotat00hoitgoog/excellentquotat00hoitgoog#page/n138/mode/1up and Many Thoughts of Many Minds: A Treasury of Quotations from the Literature of Every Land and Every Age (1896) by Louis Klopsch, p. 266 https://archive.org/stream/manythoughtsman00klopgoog/manythoughtsman00klopgoog#page/n268/mode/1up.
Misattributed

The She-Ancient, in Pt. V
Source: 1920s, Back to Methuselah (1921)
Context: Art is the magic mirror you make to reflect your invisible dreams in visible pictures. You use a glass mirror to see your face: you use works of art to see your soul. But we who are older use neither glass mirrors nor works of art. We have a direct sense of life. When you gain that you will put aside your mirrors and statues, your toys and your dolls.

Interview (<!-- most likely 17th April -->April 1935), as quoted in The Genuine Islam, Vol. 1 (January 1936). A portion of the statement also appears quoted in The Islamic Review, Vol. 24 (1936) http://books.google.com/books?ei=0_neSrrfD4K0NIPBiaAF&client=safari&id=4MnRAAAAMAAJ&dq=%22try+to+whittle+down+their%22&q=Shaw#search_anchor edited by Khwaja Kamal-ud-Din, p. 263
Disputed
Context: I have always held the religion of Muhammad in high estimation because of its wonderful vitality. It is the only religion which appears to me to possess that assimilating capability to the changing phase of existence which can make itself appeal to every age. The world must doubtless attach high value to the predictions of great men like me. I have prophesied about the faith of Muhammad that it would be acceptable to the Europe of tomorrow as it is beginning to be acceptable to the Europe of today. The medieval ecclesiastics, either through ignorance or bigotry, painted Muhammadanism in the darkest colours. They were in fact trained both to hate the man Muhammad and his religion. To them Muhammad was Anti-Christ. I have studied him — the wonderful man, and in my opinion far from being an Anti-Christ he must be called the Saviour of Humanity. I believe that if a man like him were to assume the dictatorship of the modern world he would succeed in solving its problems in a way that would bring it the much-needed peace and happiness. But to proceed, it was in the 19th century that honest thinkers like Carlyle, Goethe and Gibbon perceived intrinsic worth in the religion of Muhammad, and thus there was some change for the better in the European attitude towards Islam. But the Europe of the present century is far advanced. It is beginning to be enamoured of the creed of Muhammad.

Preface; The Sacredness of Human Life
1930s, On the Rocks (1933)
Context: In law we draw a line between the killing of human animals and non-human ones, setting the latter apart as brutes. This was founded on a general belief that humans have immortal souls and brutes none. Nowadays more and more people are refusing to make this distinction. They may believe in The Life Everlasting and The Life to Come; but they make no distinction between Man and Brute, because some of them believe that brutes have souls, whilst others refuse to believe that the physical materializations and personifications of The Life Everlasting are themselves everlasting. In either case the mystic distinction between Man and Brute vanishes; and the murderer pleading that though a rabbit should be killed for being mischievous he himself should be spared because he has an immortal soul and a rabbit has none is as hopelessly out of date as a gentleman duellist pleading his clergy. When the necessity for killing a dangerous human being arises, as it still does daily, the only distinction we make between a man and a snared rabbit is that we very quaintly provide the man with a minister of religion to explain to him that we are not killing him at all, but only expediting his transfer to an eternity of bliss.

Preface, The Sacredness Of Criticism
1930s, On the Rocks (1933)
Context: The last word remains with Christ and Handel; and this must stand as the best defence of Tolerance until a better man than I makes a better job of it.
Put shortly and undramatically the case is that a civilization cannot progress without criticism, and must therefore, to save itself from stagnation and putrefaction, declare impunity for criticism. This means impunity not only for propositions which, however novel, seem interesting, statesmanlike, and respectable, but for propositions that shock the uncritical as obscene, seditious, blasphemous, heretical, and revolutionary.

1900s
Source: The Irrational Knot (1905)

Source: Mrs. Warren's Profession & Others

Source: Advice to a Young Critic

"Rungs of the Ladder" http://books.google.com/books?id=HLpRc3rm5b8C, BBC Radio broadcast, 11 July 1932
1930s