C programming tricks

While programming optimization that makes ones' code completely unreadable is often a bad thing, there are places for it, like that one inner loop of your code that takes up 98% of the program's running time.

What are you tricks for improving performance in C, other than the obvious inline assembly or the like?

Declare variables as static so the CPU doesnt have to set aside memory on the stack in each function call. Just be sure to reset it each time.

int foo(int a)
{
    static int variable;
// ....
    variable = 0;
}