Generally I took the keys with me when leaving the house. But since there is always a possiblity of forgetting or not needing to go to the street, when I hadn't left the house before going to bed on Friday night, I made sure of switching an electric light on/off. On Yom Tov, I always switched a light, since taking the keys does not violate Yom Tov.
I trusted the Ravs on that, even though my interpretation is that taking the keys may be not a real violation, since the intention is to keep the keys with me, not exactly to take them to a certain place. Besides, even following the sages' opinion, it's not always agreed that taking a key along the street is really a violation: If someone, has the keys hanging from his neck (or any similar way), then they would count as jewels!!!!