I am certain that 95% of all readers of this blog know how to make quilt binding, but this post is for those who don't - like my friend Chris B who is making her very first quilt. She has warned me that quilt binding is in her future, so this is particularly for her.
The first, and most difficult, step to making quilt binding is figuring out how much fabric you need. I am spectacularly bad at this. I search the internet for formulas, I read books, and in the end my method consists of "make way more than you need". I figure that it is better to have too much than too little, and any leftovers can be use to bind placemats.
So to make bias double-fold binding, I usually start with one yard of fabric for a queen size quilt, three-quarters of a yard for a double size quilt, and a half a yard for a twin size quilt. This will give you plenty of binding, and then some. Start by squaring off the edges - this will make every step afterwards a lot easier:

Then take the lower right hand corner and fold it towards the opposite selvage edge:

Fold it all the way over to the opposite selvage edge, so that the resulting fold is a 45 degree angle, and, hence, the bias:

Use a pair of sissors to cut along the bias fold:

Don't worry about being perfect; you can clean up this edge later on in the process with a rotary cutter. Next, lay out your resulting two pieces of fabric so that you get a parallelogram. (You remember geometry, right?) The two selvage edges will abut each other:

Pin the two selvage edges together:

And then sew them together. Press your resulting seam open:

Next, fold your fabric in half, so the bias edge is vertical on your cutting mat. Your parallelogram will look like this:

(Further clarification on how to fold your binding parallelogram can be found
here.)
Clean up the bias edge by using your rotary cutter:

Now start cutting 2 1/2 wide strips:

Repeat until your fabric is all cut into strips. Shot of parallelogram getting smaller as strips are cut:

From a yard of fabric, you will be able to cut 12 strips. This is plenty for a queen size quilt.
Next, join your strips together to make one long piece of binding. I start by laying one strip out on my cutting mat, right side up like this:

Then take a second strip and lay it right side
down at a right angle to the first strip like this:

I use the grid on my cutting mat to make sure the strips are at a 90 degree angle. Don't just eyeball it. What your eye
thinks is a 90 degree angle just isn't. Measure. Then put a pin in it like this:

Next, draw a sewing line parallel to your pin from corner to corner like this:

It's important to draw the sewing line. Don't just eyeball it, because what your eye thinks is a straight line, ain't. Next, put a second pin parallel to the sewing line like this:

Now sew your two strips together. Sewing your strips this way allows you to sew your seam on the straight grain which is more stable. After sewing, trim the excess so that your seam allowance from your sewing line is a quarter of an inch:

Press your seam allowance open:

Join all your bias strips together the exact same way until they are all joined. I use an assembly line process and it goes faster when you have done it a few times. After you have all your strips sewn together and the seams pressed, fold your binding horizontally wrong sides together and press:

You'll have to cut off the "dog ears":

That's it! There is nothing new or unique about how I make binding; I learned how by reading books and coming up with a method that I use
every single time so I can reduce the likehood of mistakes and reduce the frustration factor. (Really important when you are impatient to get a quilt done.) Chris, let me know if something isn't clear or you need help. Miss Eileen, are you reading this???