My main mistake was rubbing the decal too hard with a felt covered squeegee after the decal mask was off. This took a little of the red ink off that had to be touched up with a paint pen. The decals also had some creases from being rolled. Let them lay out with the playfield glass or something else to flatten them for a day or two.
I also would use a straight edge to trim the decal after it is on rather than the cabinet edge. If you get the cabinet edge just right with a nice bevel than it's probably better but a straight edge is safer if you're not a pro. I bought a 5 ft straightedge from Home Depot and used clamps to hold it in place.
The top of my side decals needed to be cut before application to line up right with the front and the original look of the machine. Take your time laying out the decals on your machine before starting to apply. I used the wet method to apply and can't imagine why you would do dry - especially your first time. Just make sure not to let the liquid drip onto the bottom of the cabinet.
Like everyone says, applying the decals is the easy part if you've put in the days of prep. Good luck.