- Take a quick look at the symptoms and code and see if it's obvious

- Take a look at the jstacks and see if there's anything that stands out (lots of code stuck in the same place)

- Take a more thorough look at the code to see if anything stands out

- See if I can reproduce the issue locally

- From here it various wildly

I rarely run a profiler just because it's difficult to put it into place in a production environment (which is generally the only place these issue come into play unless you set up the conditions artificially on a lower environment). That's not to say never; I just try to identify the issue other ways first.