If you wanted to track down performance issues on a machine running Mac OS X and find out what was causing slowdowns, which command-line or graphical tools would you use, and how would you use them?
I'm interested in advice on the best tools, and explanations of how to use them - when a machine slows down or freezes up, I'd like to be able to dig down and understand what's going on, memory / disk / CPU-wise.
Thanks.