"i'm VERY new to embroidery, but I absolutely love it and am totally consumed by it. but, being "new" has it challenges. How do I center a t-shirt and make sure that it stitches straight across instead of that lovely slant that I oh so often get? is there a special tool?"
You can buy a couple of special tools but they are for mass-producing shirts. For just doing 1 or a few shirts you don't need that tool. Instead, fold the shirt in half vertically so there's a line running down the center of the front of the shirt. Make that line visible by either pressing an iron on it to create a temporary crease OR using a disappering fabric marker. Once you have the vertical line, use it as a guide for the edge of your hoop.
If you will be doing LOTS of shirts, there is a tool called a "HoopMaster" that automated lining up the design...
