Rags for RugsThere are many different ways of making rugs from rags. All of them have certain things in common, so I'll put some of the basics here.
The material for a rug should all be of the same material. I prefer cotton, but have also used wool and polycotton. The main thing is to not mix materials in the same rug, and to have all of your materials be the same weight.
I am going to divide the types of rug into "rough" and "finished" for further discussion of preparing the strips.
Rough: Rip the strips into 1-inch strips, and don't worry about threads unless you have a real wad. If so, rip them off of the material. To join them fold over about an inch of the end of the first strip, and snip a cut into the material about a half-inch long from the fold to about a half-inch from the end of the material.
Do the same thing to the next strip, and pass the end of strip #2 with the cut on it through the cut on the end of strip #1. Pass the uncut end of strip #2 through the cut end of strip #2.
Pull all of the strip through, then carefully straighten it so that the overlapping ends point in the direction that they originally pointed. It won't be as perfect as the image, this is just to give you the idea.
Join all of the strips in this manner.
Rough strips can be used to crochet rugs or to weave very rough rugs.
These should be ripped into 2-inch strips, and cut and remove extra loose threads. Fold both edges to the middle, then fold in the middle so that all edges are concealed, and press in place. They do make little devices that do that for making braided rugs, and these are usually carried in Joann's Stores. These are joined by taking the two ends to be joined and overlapping them in an upside-down "L", right-side to right-side. Sew a seam corner-to-corner, and cut off the excess. When unfolded the seam disappears. These are used for braided rugs and very finished woven rugs.
With crocheted rugs you don't really want to join too many strips ahead because it makes it easier to work with and plan your rows.
With woven or braided rugs you want to keep a lot of strips joined ahead so you don't have to interrupt your word too often.