Prints well at 0.3mm layer height, for speed and strength. Should print with finer layers, if you want, and generally can use thicker layers if you are set up for that.
A very quick OpenSCAD primer, if you have never used it but want to customize this model:
1. Install OpenSCAD :)
2. Load the included .scad file
3. Press F5 to get a quick render of the current settings. You can adjust the view with the mouse: left-button drag rotates object, right-button drag slides the object, and mouse wheel zooms.
4. Adjust one or more of the documented values in the text window.
5. Repeat steps 3 and 4 until you are happy with your design.
6. Press F6 to fully compile the model. This may take a very (VERY!) long time, depending on your settings and your computer... Go grab a snack or a drink...
7. Use the File/Export menu or the "STL" toolbar button to export an STL of the current model.