I don't know what the proper way of sewing patches on clothing is, but here is how sailors are taught to mend.
The problem with just sewing a patch over a hole is your stitching the patch into the weaker material that caused the hole. Sew a large patch onto the back of the material like so.
Then sew a smaller patch over your hole, through the weak material, into your new patch.
Seems like a lot of work? I'm going to start experimenting with using my good shop glue to mend clothes. Stand by for updates!