A lot depends on whether or not the print is off grain or not. If it's off grain, I use Best Press lightly before cutting out anything. Otherwise, I use it after the block is completed. I don't like using starch. It is too stiff and I lose the feel of the fabric with it.

I find with careful cutting, sewing and pressing along the way rarely do I have to square a block. About the only thing I square is half square triangles. I make them larger and then trim.

I will use starch at times before I cut. To starch it I lightly spritz the material and then roll it up and let the starch absorb into the material. I do something else while the material is mellowing. The material is only slightly damp when I press. I always press my material before I cut it. I use a dry iron as I don't want to add the moisture that steam gives. I press each seam as I do it. This allows me to have very sharp intersections and I think keeps things more true.

When cutting my fabric I try to keep the grain as true as I can. The more off grain you are the more likely the piece will distort. Some shapes other than squares and rectangles are going to have some off grain sides which is one of the main reasons I starch which will stabilize them some.

I generally am not starching the finished block - I starch the fabric before I cut. And I love the control that starch gives - I get more accurate cutting and seams with starched fabric. I am pressing each seam as I go as well as the final block, and I do use steam.

For squaring up, I like to find something in the block that marks the centre or aligns somewhere. I really like using a rotary cutting mat for squaring up so you are not picking up the block, just turning the mat.

Good for you for squaring up - took me a long time to see that this step really helps ensure your finished quilt goes together well.