Do you pull a thread or tear it? I pull threads, my friend who also quilts, tears her fabric.

If it is a big enough piece - I will tear it.

I have up to a two ft ruler that I use :D:D:D

I use a ruler.

But using a ruler - how do you know you've got it straight with the grain? Or isn't that too important in quilting?

I use my ruler. As long as I have a 90 degree angle to the salvage edge it is OK.

Exactly what I was going to say!

I do same at littlehud and lucy inthe sky.

When I made clothing, I always pulled a thread to straighten fabric. In quilting I usually use a ruler like others have said. The grain does not have to be as perfect in quilting, but should be in the general area.

That is what I do as well.

Arthritis prevents me from pulling a thread or tearing, so I use my ruler & rotary cutter. First, my fabric must be washed and pressed. What I do is hold the selvege edges together at eye level, hands about shoulder-width apart, and look at the bottom (nearly-folded) edge. When this bottom edge lies straight to the eye, I use that as my guide to straighten the edge with rotary cutter/ruler.

If I am off, there will be a "kink" in the cut strip that either looks like a "v" or a "^". If that is the case, I start again.

This works for any fabric, the expensive LQS types, or the cheaper types from a discount store. I never rely on the fold being exactly parallel to the selvege, nor do I rely that the selvege is perpendicular to the crosswise threads. I used this method when I taught quilting, and it has never failed me.