Proper method to check transmission fluid?

I have an 09 Tacoma Automatic Transmission 2.4ltr Engine do I check the tranny fluid while engine is running, what is the proper method.

 

Engine running at operating temperature in park.

 

On tranny's with a dipstick with cold and hot marks, pops told me to always measure with the hot mark at operating temperature because ATF expands with heat and you want the ATF at the proper level when at normal operating temperature. Use the cold mark after a flush to get you close to where you need to be once the ATF warms up. That being said, I find it a PIA to get a good reading when the ATF is being pumped through the lines! RIP pops.

 

Check the automatic transmission fluid when the engine is at operating temperature, engine running at idle and vehicle on level ground.

 

And for future reference it is a 2.7 liter engine, Not 2.4 liter.