I like to make cross-grain binding. I generally cut 2 1/2" width of fabric strips (or 2 1/2" strips from left over fabric if I'm making a scrappy binding). To work out how much binding to make add the length of all four sides together and add at least 15" (this will make extra long binding, but I would much prefer too much than too little!) Divide this by 42, and this will give you how many strips of fabric to cut. I always round up here (so if it's 6.4, I'll cut 7 strips).
I then I cut the end of each at a 45 degree angle, using the line on my ruler.
Once all the strips have been trimmed at an angle, I sew them together using approximately 1/4" seam (as long as they're sewn straight across the overlappy bits it will work regardless of seam size)
Next, I press the seams flat, and then press them open:
You can trim the excess side bits off now.
And then fold the binding over lengthwise (wrong sides together) and press along the length of the binding:
SEWING BINDING TO QUILT SANDWICH:
I don't pin my binding to the quilt sandwich - I just match raw edges as I go. I leave a tail of about 10" at the beginning, and do a few back stitches to secure the start of the seam.
Keep sewing along until you get almost to the edge of the quilt - stop 1/4" away from the edge of your quilt top. I do this by sight, but you could measure and mark if you prefer - but if you go a bit close its easy to unpick a stitch or two in the next step. Stop you sewing machine in the needle down position.
then turn the quilt 90 degrees, so the binding is running at a right angle to your foot (the 1/4" mark should also line up with the next edge of the quilt):
Backstitch away from the quilt top (I usually have at least 3" of batting and backing around the quilt top to facilitate this step):
Make sure you've backed far enough off that you can fold the binding up:
And then down so that the top is lined up and the raw edges line up:
Then simply start stitching back onto the quilt top using a 1/4" seam allowance as before. Repeat this for all four corners.
To join the ends of my binding strips, I use the great tutorial by Sarah at Fairy Face Designs. It works perfectly every time.
I machine sew my binding at the back, using the reverse method by Marianne at The Quilting Edge.
Hopefully this makes sense!