Checking your engine oil, warm or cold engine?

Dan67 is right – the simple answer is to read the manual. My car is to be checked with a hot engine that has been switched off for 5 minutes. I've had other cars that should be completely cold.

I always fill up the oil to halfway on the dipstick – no need to fill it to max, which puts extra pressure on the seals etc.

According to the manual for my bike, check after 15 minutes of running.
Being a sight glass, when the engine stops and if I'm quick getting it on the centre stand, I can see it settling. I normally wait until it's settled (2-3 minutes) and take that as the oil level.
I do the same for a car (except it doesn't go on a centrestand, obvioulsy, but someone was going to mention that). I've always assumed that you check the oil under operating conditions.