I thought since this is what I was doing this morning, I would share how I do it.
First of all, I almost always use 2 1/2 inch binding. It's actually a little too much, but I like to be able to cut up the extra into 2 1/2 inch squares, so I just go with that.
I first cut enough strips to go around my quilt. How do I figure that? Well, first I find the perimeter of my quilt. For example, if the quilt is 40X40, the perimeter would be 160" (40+40+40+40). Then, I figure 40" of usable fabric for each WOF (width of fabric) strip, so I would cut 5 strips because I need the extra to go around the corners and the extra that hangs over at the beginning and the end before you finish them together.
To sew them together, I first lay down the first strip right side up.
Lay the second strip right sides together at a 90° angle.
You can pin it together, or not. If I pin, I pin away from where I'm going to be sewing to just keep it together and straight.
Rotate the piece clockwise to find the spot that you sew from.
Sew a couple of stitches...
Then line up the opposite end. You can do this several ways. My table has a "0" that is in the position of my needle, so that's how I line it up.
There are products like the Angler 2 that you can put on the bed of your sewing machine that help you to keep the strips at the right angle. (There's another one that's just like it, but I can't think of the name!)
You could draw a 45° angle line on the top strip.
Or, like me, you could just "eyeball it."
Make sure when you come to the end, you come out exactly where the strips cross.
Lay the next piece down and place the next strip right sides together on it at the 90° angle.
Take the sewn together strips to the ironing board.
Check to make certain that you've done everything correctly. Believe me, I've messed up SEVERAL times...especially if its been a long time since I last put on binding, lol.
Trim the seam to 1/2" or so. You can see I left this longer than 1/2". For me, it seems that it's easier to work with when the seam is longer.
Press the seam open.
Trim off the little tabs...