So I decided to personalize my jeans a little, and give them a more punk look using some awesome neon thread I found lying around. They already had patches in them, but you can add your own patch if your jeans don't have a one.
Just cut a hole in the patch, in any shape. (I suggest keeping the hole either small or narrow to avoid the thread getting too wild, especially when your not wearing them.) Then, with your needle and thread, start from the inside, on one side, and bring it to any other side. Keep going until you get this criss-cross pattern, make
them straight lines if you want, sew zig-zags, GO CRAZY :D! When your done, tie it off and hide the tail under the remaining part of the patch.
Note: remember to keep the thread taunt, but not too tight. You might want to wear the jeans as you sew or try them on periodically. If you're going to be using a lot of thread, use two smaller pieces of thread instead of one big one so it would be easier to tighten.
You could also just do it on a random place to add a little flair. Keep in mind that you won't get the same result as if you did it with a patch.