The only time counterfeiters get caught is when they counterfeit $50's and $100's and go buy big ticket items...
Counterfeit $20s, dress like a working man, go to a convenience store at 4am and buy a cup of coffee and pay with a counterfeit $20. Do this for the next 4 hours. Only ever carry one counterfeit bill on you when you go to a store. Park your car away from the store.
Smile for the camera.