A State could require mandatory enrollment for all residents over the age of 18. Non-citizens would be required to register, but would be given a distinctive ID. Citizen felons who are not incarcerated would not be registered to vote, but would be given a standard ID.
Since registration would be tied to actual residence, there would be no need to depend on the census, and districts could be updated on an as-needed basis, as is done in Australia.
Or in Germany, for that matter. In Germany, there is mandatory requirement to announce any change of address (while doing that, they just fix a sticker with the new address on yout ID). Everything else (notification of tax authorities, vote register update, taking you off the records in your previous location of residence, etc.) is done automatically, so its actually quite easy and citizen friendly. One drive to the county office, filling the form, 2-3 minutes inside while they record your data, print out and fix the sticker to your ID, and that's it. No fees, since registration update is mandatory.
