Multiple cuttings will improve the chances for success. Some Prunus can be difficult to start from cuttings and chokecherries are noted for that.
In general, I start softwood cuttings in pots in plastic bags, out of any exposure to the sun, of course. Matthew gave you good advice. I would just add that you should try both hardwood and softwood cuttings and may want to try slightly different times in the spring for softwood and differing times in fall or winter for hardwood (hardwood in the ground in winter or kept in the refrigerator until early spring).
I think most Prunus will have better success with softwood cuttings, however, there is a lot of variance depending on variety.. I have also read advice for starting (softwood) cuttings timing that is tied to how mature the fruit is, with some advice linking best success to cuttings (for Prunus, but not specific to your variety) that are taken between fruit set and fruit maturity.
Also remember that you are trying to propagate the top set of the plant, so root suckers should be avoided as sources for the cuttings if you are not sure that it has not been grafted.
Since you have an established plant, you should have a chance to repeat attempts under slightly different conditions, if your initial trials don't work.
