determing reflection points

I have Apogee Slant 6 speakers and have been room tuning for some time now but... I was wondering how I determine my 1st reflection points (walls & ceiling) since they are bi-polar so that I can better evaluate how to tune better in the future, can the forum members help with suggestions on how to explore this?
I think one way is to sit at your listening position and have someone hold and move a mirror along the wall and when you can see the drivers, that's the first reflection point.

It's a very rough approximation but it should do in most cases.

All the best,
That's exactly the way to do it and is more than a close approximation. To augment that, once you see the first reflection point, keep sliding the mirror down the wall until you see that other speaker and treat that spot as well. Rinse and repeat for the other wall.
Thanks for helping me with that, I think I've got it. additionally, any way to determie reflection points on the ceiling too?
Here's a calculator for floor and ceiling reflections /audio/ floorbounce