I square up the blocks, so I guess I trim them. I am doing a 6" block quilt that I might not square up, a full size, very patterned bright fabrics.

I do my best to make them the same...

if for some reason i have a block that is a few threads off, i don't trim down all the other blocks. i just make sure to line that block up with a good one, and sewing an exact 1/4 inch seam. the skinny one would have a tad less than 1/4 seam of course but as long as it's almost enough, it's fine.
by that i mean i line up three sides exactly and the skinny one doesn't fit to the raw edge of the really square one.

I am glad someone asked this question because I trim my blocks as I go. I didn't know if I was wasteing my time but I quess not from the replies.

I square up as much as possible. I've found if a block is short I can fudge the size when adding the sashing.

I trim all my blocks prior to piecing. It makes a big difference in how it turns out.

I cheak my blocks and tend to square them up exact. If any of them are undersize, I mark those and adjust the seam allowance. As for points. I adjust the seam allowance to make sure the point is in the picture.

Learned a long time ago (and believe me, it wasn't a lesson learned easy) the success is in the prep work. The better care you take in the prep, the better your result will be.

I trim and square exactly, and for some blocks that means more than once as the block grows. My tops are always flat and need very little squaring up before sandwiching so, for me, it's well worth it. Do what works best for you.

I trim because as a beginner whatever I can do to insure some accuracy is important. Do what I can do well and unstitch or trim as needed.

I learned that the hard way doing SID.