Don't let the sewers in your life know about this...
If you have ever bought pre cut patches lately you know the $$ has gotten crazy. Years ago I bought a yard of cotton twill (sales lady said what it was, I have no clue) and it lasted FOR EVER :) but i can't remember the cost than. Well I just bought 1 yard of patch material and half a yard of cleaning patch material, with tax $12.50... Compared to the pre cut bag of 100 patches at $7.95 locally YIKES!!! You can also "hover" around the sewers and grab up the scraps of any all natural fiber fabrics they use :) , this makes good testing patches. If you find a fabric that works for you, buy more :)
One thing you need to look for is 100% natural fiber cloth, While I haven't shot a poly blend myself I have been at the range with someone that did, melted patches don't shoot well... When you get your new material home you will want to wash it to get the sizing stuff out of it. This gives you a better feel for it's thickness, thickness is very important and takes some testing to get right.
Patch thickness is yet another cog in the machine of accuracy. There is no magic thickness, it's part of the "Patched Round Ball (PRB)" chain that needs testing to find the right combo that works for you and your rifle. PRB chain consists of your lube, patch and round ball of choice. Some barrels like different things and you have to be flexible and test products to find the "load" that works for you. More on lubes in another topic :p
If you already use a pre cut patch that works for you, say Ox-Yoke brand, they should have had a patch thickness on the label. This will give you a starting point to getting your fabric at the store. Remember that the stuff has a sizer in it and that flattens the fabric a bit. Take the patch with you and ask the counter helper to direct you to something close to that material. Get as much as you need, smallest amount for testing, wash it, and cut into strips or squares as you like. Hit the range and blow smoke :) Find and read your patches to make sure things are going well.
I'll get another post on reading patches in a bit. Have to wash this batch of cloth :)