I use bumpers (so all plates from 10-25kg are the same diameter).
I use this little dude:
Amazon.com : Dead Wedge (TM) - Deadlift Jack Alternative for Your Gym Bag - Raises loaded barbell & plates for effortless Loading/Unloading - Perfect for Powerlifting, Weightlifting, Crossfit, Home Gyms, or anyone performing heavy lifts such as the D