* You are as neat as a pin. (This is a classic and very common simile.)
* You are as neat as a whistle. (This implies efficiency and precision.)
* You are as neat as a freshly-ironed shirt. (This emphasizes orderliness and crispness.)
* You are as neat as a well-organized library. (This emphasizes a systematic and detailed approach.)
* You are as neat as a freshly-baked pie. (This suggests a sense of pleasing perfection.)
The best simile for you will depend on the context and the specific qualities you want to emphasize.