This seems like an easy question, but I'm sure we can all learn from everyone's special ways to straighten the fabric, line it up, and what rulers and cutters we use, and why. It may have been discussed before, but its always a learning tool.
While cutting fabrics for the brick swap, I realized my idiosyncrasies. When I'm cutting two strips, I "scratch" at the top strip if they don't quite line up until I get two perfect alignments. I use lines on the rulers to get a square cut, lining up the bottom edge before cutting the side edge. That way I'm assured of a straight cut. I ALWAYS use caution when rolling that cutter, and have yet to cut a finger.
I straighten the fabric before cutting by folding selvage to selvage, holding the fabric up in the air, and moving one side of the fabric until selvages are even. This may mean that one cut end needs to be cut to straighten, but I feel that is a small sacrifice for my precious fabric.
I use a 24" ruler with sandpaper dots on the bottom and a grasp handle on the top. I LOVE LOVE LOVE the June Tailor Creative Cuts. I have the older styles, one each of the 1/2 cut and the 1/4" cut. I wonder what I ever did without them.
My rotary cutter of choice is Fiskars. I just bought a pink one ... my favorite color! I go WAY back in the world of rotary cutters and rulers. My ruler is a Dritz, and I have a very old Dritz rotary cutter which is now used for paper cutting. The lines on the ruler are brown, as is the rotary cutter. I find it difficult to use anything else.
How about you? :D