Not much. The fan is going to spin to cool down the machine, if you're engaged in CPU/GPU strenuous tasks. When the fans get high, open Activity Monitor (Applications>Utilities folder) and use the CPU tab and then sort by CPU %. If something's taking up more than, say, 18-20% of your CPU, then you can try to quit the application or process that may be causing the unit to heat up and the fans to increase in speed.
If everything looks OK from a CPU standpoint, try resetting the SMC (if the folks at the Apple Store didn't already try this).
Install iStat Menus and use that to monitor what the fan is doing. Default idle speed is 2000 RPM. Will ramp up to 6000 RPM if things get too hot in there (which you can monitor too).
thank you for your help. i have a genius bar appt this afternoon. genius bar ran diagnostics a couple days ago on the fan and said it was ok. the fan will kick in loud even if all im doing is viewing email or on the internet. next time i will check the activity monitor to check cpu usage. im frustrated.
Activity Monitor will only give a partial picture of what's going on inside, since the CPU isn't the only hottie in there; the GPU can also pack a wallop. If you don't want to pay for the new iStat Menu (used to be free), try Marcel Bresink's free Temperature Monitor: http://www.bresink.de/osx/TemperatureMonitor.html You'll be amazed at the sheer number of temperature sensors inside these things.
And as to WHY it is running hot, try this: http://support.apple.com/kb/TS1473
Yes. At Genius Bar the tech reassured me that depending on what the laptop is sitting on and what I'm running will affect if/when the fan starts. I assumed the fan would be silent- after all this is an apple :-). I have the MacBook Pro 15" with retina display-he said the more compact the computer is-and this one sure is-in combination with the display being a few times greater in resolution from my old pc-it's a powerful machine in a tight package. Cooling needs are going to kick in. So he pulled up the activity monitor and played music and started a game of chess-computer against itself-at the highest difficulty-and had me doing other things in it. Fan didn't start for some time. And when it did it was "normal". I had been told to reinstall the op system by
Apple tech on a previous visit. I told this latest rep I'd been told that and he sort of didn't seem to think it necessary-but he did it while I was there anyway.
So-really-since my initial "***" I can hear the fan and I'm not really doing anything-I've heard the fan start rarely since. I'm convinced its fine. He showed me how to take a screen shot of the activity monitor if I was ever concerned-so they can see what program is hogging resources and may be the culprit. I've not needed to do that.
I felt much better with my last rep-he took the time to explain things and be patient with me. He had a 17" Mac that isn't made anymore and he can hear his fan when gaming for awhile-even though the computer shell is a lot bigger.
Hope this helped a little :-)