One of my bikes has the e clips and the other the rings.
The E Clips are much easier to get off with the proper tool. You can get the tool and clips in a pack usually.
The others I do as suggested above. I use one straight pick and one bent. I use one to hold the clip in place and the other to split the ring and pull it off.
13 Vision Tour - PCV, Top Filter, Stage 1 Pipes, TW @ +4, Metz 888s
08 Vision Street Premium - VFC, Top Filter, Stage 1 Level 2 Pipes, E4s
Past Vic - 07 KP Tour - Stage 1, S&S Intake