I really try hard not to use my flash if I'm trying to capture the moment. If the flash fires and makes everything bright you really don't get a "feel" of the time of day or the lighting when the picture was taken.
Kaylee and her friend were watching their movie late at night. You can see in the catchlights of their eyes that the only light source was the TV off to the side. They have very small catchlights! I didn't want a big bright flash in their face because then it would look like mid-day. SO I turned my ISO up to 1250 and shot away....
To me it reflects exactly how my eyes saw them up in the loft that night.
Same with Rebecca reading by her lamp. If the flash would have fired you wouldn't have even been able to tell that a lamp was on. It would also have alerted her that I was taking pictures.
Birthday cakes are another perfect time to turn off the flash and capture the mood of the candles...
Pictures don't always have to be nice and bright. The shadows and lighting help in portraying the moment. SO, my photography tip is to turn off your flash and try to achieve the lighting as you see it!