The scale of crosshatching is up to you - whatever fits best in your quilt. I think it's best to quilt straight lines about two inches apart in both directions of the cross hatch and then stitch between those lines for a finer look. If you stitch lines close together to begin with, it may pull the fabric, so that's why I start with a larger grid. When you reach the end of a line, turn and stitch down to the start of the next line and then turn and start the next parallel line. Or you could tie off each line if you don't want to travel, but I find that a bit tedious. If the crosshatching is near the edge of the quilt, you can always stitch beyond the edge a bit, then turn, travel to the next line and sew the next parallel.
Kathy