Taken from an article at Knut Erik Evensen’s site: 
Some ideas for best common practices when mastering DCPs

For the very brave, he also has instructions on making your own DCP using free or Open Sourced programs (EasyDCP, for example), but he also has a very reasonably priced service.

If a movie uses a workflow like the movie Inception where there is no Digital Intermediate (DI) and the film is color timed photochemically in a film lab, the color timed print has to be scanned and fine tuned for 2.6 gamma 12 bit linear to make the DCP. Otherwise the 35 mm print has to be screened. In no way can the offline edit or a SD video tape be used to make a DCP for theatrical distribution.

A DCP should be made from the DCDM with correct XYZ colorspace and 2.6 gamma made from the Digital Intermediate (DI) that has been graded on a P3 color space projector with 14 footlambert of light. The DCP is normally made from the emulation of how the 35 mm print will look on a digital projector. This emulation is baked into the DCDM and the DCP is fined tuned for 12 bit linear. The resolution should be 2048×858 or 1998×1080.

Continued at: Some ideas for best common practices when mastering DCPs