The Flight Crew's failure to properly secure the aircraft at the end of the day resulted in inappropriately positioned Generator Control Switches the following day.

Narrative

Upon arrival at the gate after an uneventful flight; after shutdown and passenger deplaning; my First Officer asked me whether we should 'put the airplane to bed' (meaning run the SECURE checklist to an unpowered state). The SECURE checklist is not specific. We are both international category pilots; and this was the first domestic trip we had flown in some time (in my case; about 2 years). I have flown very few purely domestic trips in the past 8 years. In that time the procedures for securing an aircraft at the end of the flying day have changed. Also; formerly; this station had permanently based mechanics; a situation that has also changed. So; I told the First Officer I would ask a station rep how they wanted the aircraft left. The only person to ask was a passenger service agent. I asked him whether he wanted the power ON or OFF - he told me to leave the APU running. I told him the APU was already off but that external power was still connected and he said to leave the aircraft just like that. So; we did. When we returned to fly the same aircraft out the next morning we eventually discovered that someone had left the aircraft's electrical system in a very unorthodox and potentially damaging configuration; the generator control switches had been turned off. (This manner of configuring the aircraft is; to my knowledge; not a part of any towing; ground ops; or even normal maintenance checklist; so someone was 'winging it'; so to speak.) This situation led to certain malfunctions that are described in a separate report; being that they occurred the day following our arrival. I later discovered that our company now requires crews to leave aircraft in a powered-down state on the last flight of the day at all non-maintenance stations. Neither of us was aware of this change; and we had not encountered a need to do so since; being on international routes; maintenance must run checklists after arrival; so there is rarely; if ever; any reason to power-down an airplane. If we had DE-powered it; it is unlikely anyone would have to touch anything in the cockpit. Lesson learned; I will fly the same trip again; and will certainly de-power the aircraft before leaving it.