How do you like to check for vac leaks?

I know several folks out there have methods to look for vacuum leaks using various flammables. I want to know what your preferred method is and why. I've heard of propane, starter-fluid, brake-cleaner, wd-40, etc.

Do they all work the same way? What effect are you looking for? How big an increase in rpm's do you expect when you find a leak?

I don't really suspect I have a leak right now but I am running a bit lean and thought it would be wise to check for leaks before going over-rich to compensate.

Thx,

-Chris

Thanks, Denny! I like the propane enrichment trick to check if you're too lean... I hadn't thought of that.

-Chris