I ran around for weeks looking for the perfect container to refill the iron at my church sewing group. I wanted one like I have for my own iron, but never found one. One day someone left their bottled water in our sewing room, just one of those simple disposable water bottles like you can buy at any store by the case. The mouth is small and easy to fill the iron, it holds 3 refills, and I don't have to tote the hot iron to the bathroom to fill it!
I use a strip of masking tape at the 1/4 inch mark to keep my seams perfect.
When I'm piecing, I try to plan my seams so that they will 'nest' when I go to sew my blocks together. Also when I have seams coming together in the middle, I iron them so they twirl around the center. To do that, I've had to learn to refrain from backstitching.
I've learned that when you ask a friend (or a husband) for their opinion, it's OK to NOT feel you have to take it as gospel. It's THEIR opinion... it's YOUR quilt! But I've NOT learned how to convince THEM that it's ok....
I have no idea if this is common knowledge, but I use two rulers when cutting. I am a right-hander. I use one ruler to measure from the right edge of the fabric to my cutting line, and I then butt my 6x24" ruler against the left side of the first ruler to make my cut. That way I always have the bulk of the fabric firmly under my ruler where it can't slip when cutting, and is especially useful when cutting narrow strips.