Dry your fabric in the dryer, this will help make sure it has done its strinking.
When you are done washing your fabric, you need to cut it to the width you want. I sudgest making it between 27-32 inches wide. Rember you are going to be hemming it so I would make it about 1.5, two inches wider than you really want it. Depending on the width of the material when you buy it, you may be able to get two wraps out of it!
Now you will need to hem your wraps edges. Some people like to iron their seams first making it a bit easier at the sewing machine... I am too lazy and I dont do it. As far as thread goes, get the colour you want- most people like to get a colour that is the same colour as their fabric. If you are dying your wrap (I will have instructions soon on how to dye a wrap soon), then you can buy a white cotton thread and it will dye up nice. I always use Gutermann's 100 percent cotton threads. They are very strong good quality threads.
At the sewing machine I fold the edge twice this way you are not seeing the raw edge
|fold once fold again|
My sewing machine has markers on it so I can make sure that the seam is the same width the whole way down which is why I dont iron it first. I sew a bit then I fold the next stretch, sew, fold, etc.