Relax. This will cause you to shake less, and be more accurate.
Get comfortable. Support your body and firearm as much as possible with bone structure. Use your muscles in a way that will make them all as comfortable as possible. This will make you more structurally sound, and more accurate.
Clear your mind and focus on your front sight and your target.
"Laws are not the answer. We have laws against murder. We have laws against kidnapping. We have laws against extortion. And murder, kidnapping, and extortion are on the rise. The answer, it seems to me, is wrath. Let the thug take his chances with an alert, prepared, and angry citizenry. It may very well spoil his whole career." - Jeff Cooper
"The defence of one's self, justly called the primary law of nature, is not, nor can it be abrogated by any regulation of municipal law." --- James Wilson, Wilson, Of the Natural Rights of Individuals, in 2 The Works of James Wilson 335 (J.D. Andrews ed. 1896).
Self defense is a natural law, more important than any law penned by mankind. Owning and carrying the means to defend yourself, with lethal force, if necessary, follows.
- Rudyard KiplingNow this is the Law of the Jungle,
as old and as true as the sky;
And the Wolf that shall keep it may prosper,
but the Wolf that shall break it must die.