How many times have you done the good old print_r($var); just to find out what’s in the variable?
I have been using the devel modules for age’s but it still surprises me what you can find if you just look at some code every now and then.
The devel module comes with a few great functions which you could use instead print_r();
kpr() function
Example:
kpr($node);
Output: 
dpr() function
Example:
dpr($node);
Output: 
dvr() function
Example:
dvr($node);
Output: 
Looks better then the print_r output. If you know a better way leave a comment and let us know.