I'm the last person who should be giving advice on accuracy but... I can definitely support Endaris' advice. To get better accuracy, play maps that are less challenging on your aim and reading. If you're playing a hard map and have to focus all your attention on reading and aiming circles, there's little attention left over to focus on practicing accuracy. This is the reason why I have the lowest acc on this side of the galaxy--I've almost exclusively played to pass hard maps instead of playing maps accurately.
Also, be aware of what OD the map you're playing is currently on. If you find yourself getting almost no 100's on OD 7, then maybe play maps with higher OD, otherwise you won't get any feedback on whether you're hitting the circles accurately or not. : )