When piecing, I was taught to press the seam towards the darkest color piece. Thoughts??

That's what I normally do but right this minute I"m making a 5 strip rail fence pattern and I'm going to press those seams open since there is no one direction I want to press.

I prefer that method, but it is not a hard and fast rule. Sometimes the direction can interfere with locking seams.

In fact, some quilters press all their seams open and if you machine quilt reasonably close, this is likely just fine as the quilting reduces stress on any individual seam. However, if you are going to quilt it wider or tie it, I'd still recommend pressing the seam over.

i press to the dark and then move if the seam locking is a problem...

I press open - it works for me and my process.

Open. I hand quilt and pressing to one side makes it too thick to hand quilt through.

I always press to the dark side, unless the pattern tells me differently.

I was taught to press for "ease of construction", but it is preferable to press to the dark when possible. Also, if there is a lot of bulk, I will press these seams open so the block will lay flatter.

This is my method as well and it has always worked for me.

I do all of the above..you just have to pay attention and do the best you can for THAT project! Every project is different.