That's not a stupid question; it's one of THE most essential ones for successful lapband users. Props to you for getting there early in the process!
For me, if I'm able to eat "too much" at a sitting, then it's time for a fill. My definition of "too much" is a volume question--basically about the size of a tennis ball or a little less. A second indicator is just stepping on the scales. If I find my weight trending the wrong direction (and I'm not eating too much sugar!) then it's time for a fill.
The band doesn't really stop my getting hungry; rather it makes me feel full quickly. I've embraced real hunger as an opportunity to change what I eat. Because every time I eat a reasonable quantity of something healthy, I am rewarded with a feeling of satiety. That feeling of fullness reinforces my enjoyment of healthy food.
That being said, I've had my band for a loooong time, and everybody's journey is different.
Let me interject that I've never, ever been able to remember things like how much my band is filled, when my last fill was, etc. My fill doctor is great about keeping up with this info. It's important to have that on record somewhere.
Incidentally, it sounds like you are doing really well! Congratulations! Enjoy your success--I'm enjoying hearing about it!