Don't let the bugs in the first place! Easier said than done. But it stands to reason - less bugs in , less bugs to remove.

Experience teaches you how to avoid the common ones. When you have some tricky problems heavy duty tools definitely help - unfortunately in many cases I havent had these so I've had to create methods of debugging with ICE or logic analysers. Having an led blink is the simplest, spitting messages out the serial port is probably next in line. Using a simulator is probably next - 'cos we're starting to get desperate! Failing these methods, then you need to get a little creative. Whatever you do, you need to collect evidence by doing tests. Even if a test fails, that's more evidence. Just like the crime shows on TV, collect enough evidence and the perpetrator is nicked.