How is an off-field landing accomplished at night?
Off-field landings at night are inherently more difficult and hazardous than in the day because depending on conditions you may have no way to tell what is down there. Unless you have decently strong moonlight all unlit terrain will be completely black, and you won't be able to tell forest from field. This is why it's critical to protect your night vision, it gives you a chance to see what's below you. If there's a highway down there that may be your best option, but if you're in a sparse area on a dark night you have to pick a spot that's into wind and hope it's not badlands. Even then it's still survivable if you have good technique, keep positive control of the airplane and reduce the airspeed as much as you can before impact, without stalling of course.
Aiming for clusters of lights sounds good at first, but that usually means buildings or parking lots which are not good choices.
The best way to de-risk this is through good flight planning. Choose a flight path that goes over friendly terrain: adding 15 minutes of flying time is worth it if it means you are over fields rather than rough terrain or water. Study the terrain using google earth or a similar tool. If you have a GPS you could even put good off-airport landing sites on your map. Give yourself extra altitude, and keep practicing your forced landing technique.