Here is a lovely but very simple quilt top made out of Japanese fabric. And there are really a lot of ways you can quilt this top, and the first way I would think I might approach it would be a technique called 'stitching in the ditch'. So, that's where you're going to sew along each of the seam lines. And that quilting is really not going to be noticed very much, because it's just going to sink into the seams. But it's going to emphasize the squares, which is one way to do it.
Another way to do it would be to use masking tape, and let's say we mark it on the diagonal. Masking tape is a great tool; you can sew right along the edge, and I would actually make it longer to go all the way. And you can sew on the other side, if you want it to be as little as an inch apart. They also have different widths in masking tape. If you can find two-inch masking tape that's even better. And then when you're done you just rip it off, put it next to the line of stitching you've just done and sew your next line. So, on the diagonal would be another really nice way to quilt this top.
Another way to do it would be to use a stencil and a chalk pencil. For that you would lay your stencil; you'd get the right size stencil for your quilt block, lay it down, take a chalk pencil, and you want to make sure that this is something that's going to be removable--no permanent lines when you're marking quilt tops. And you're going to just go through all the lines. And you'll see, we have a nice chalk line that after you've stitched along it it's pretty much going to disappear. And if it doesn't go away with just rubbing you can take a little wet cloth and it'll definitely disappear.
Another nice tool is a chalk-o liner. If you have a stencil, the straighter lines, or with curves, it's the same idea. It's just maybe a little bit neater, and this also just brushes away.
There are many ways to mark quilts and with all of them, the most important thing is to make sure it's removable.