One photo per day.
Shoot all you want, but pick only one for the project.
No shooting ahead. Day-of photos only.
No using old photos to make up for missing a day. Day-of photos only. If you miss a day, you miss a day. It sucks, but it’s rarely if ever fatal. Just pick it up again tomorrow.
Take pictures that resonate with you. Worry about other viewers some
other time. Thirty years from now, you should be able to look at the
image and say to yourself “I remember where I was, what I saw, what I
was thinking at the time.” Not “that’s a technically good shot I barely
Shoot with a DSLR or other dedicated device. Use a cell phone only when you don’t have another option.
Leave the house. Whenever possible, go someplace you’ve never been. At the very least, see an old place with new eyes.
Take pictures as they come. Favor the spontaneous over the carefully-arranged, “professional” image. If you’re setting up off-camera strobes or slapping on filters, you’re seriously over-thinking things. Even tricks like a shutter speed long enough to require a tripod can be taking it too far.
When I first started this project, all the rules were mandatory. However, after actually trying to make it work I found that some of the requirements were getting in the way of the project’s goal. In particular, the quality of phone photos (while not up to what you can do with a good DSLR) is now good enough to work for a project like this. Further, you can take a phone into some places that won’t allow more serious equipment.
For other approaches, consider the possibilities on the links page.