Six ways to be a great actor!

1. Speake the speech, I pray you, trippingly on the tongue; but if you mouth it as many actors do, I would rather the town-cryer spoke my lines.
2. Do not saw the air too much with your hand, but use all gently - for in the very torrent, tempest, and whirle-winde of passion, you must acquire a mood that may give it smoothnesse.
3. Do not tear a passion to tatters, to very rags, to split the ears of the groundlings. I could have such a fellow whipped! Pray you avoid it.
4. Let those who play the clowns do no more than is set down for them, for there be those that will themselves start to laugh, to prompt some bored spectators to laugh too. That's villainous.
5. Suit the action to the word, the word to the action, with this special observance: that you overstep not the modesty of nature.
6. Remember, the purpose of acting is – both at the first and last – to hold, as it were, the mirror up to nature.

(A note tells us that the 'groundlings' mentioned above are the standing members of the audience)

From Hamlet, Act 3 Scene 2