Room Acoustics: Where to place the squares?

The little squares are only good for damping higher frequencies. If you're going to do it by ear then use mirrors to decide placement for the reflective points. From your listening seat you put the squares where you can see the reflection of the tweeter on the mirror you tack up.

Reflections points from speakers yes. The importance will be be effected by proximity and wall material. For instance my speakers are ~ 10’ from the side walls and because of room geometry I don’t need any.  What is your room size and speaker position.

How many and how big??

Of course people will advise you to put them at 1st reflection points but honestly I find that alone this is never enough.  You need to have a critical mass of room treatment before you get a noticeable benefit IMHO.

Spread it around!

Of course people will advise you to put them at 1st reflection points but honestly I find that alone this is never enough.  You need to have a critical mass of room treatment before you get a noticeable benefit IMHO.

^To cut down the decay time ~ I agree^

But to cut down the early reflections is another matter.

The specific goal was not stated by the OP, however some measurement would be useful before ordering the stuff to address what the exact goal is, and where the OP wants it to end up at.

(i.e. what specific problem is the OP addressing?)

I believe REW does the RT60 decay time, and also the early reflection as a correlation. Is this OP doing that?

But to cut down the early reflections is another matter.

My point is, if you don’t have control over the room decay you won’t notice first reflection point absorption. I’ve treated several rooms, and never have I heard a big improvement by treating first reflection points alone. Only once the room was better treated did those panels suddenly become worthwhile. We pay too much attention to first reflection points, IMHO. It’s not, alone, going to do much good.