It varies prety heavily. In Spirit racks, where I have th tracks to mess with, I'll just drive around fo hours shooting boulders and trying(read:failing) to catch rabbits. Somethimes I'll chase explosive trains, but I'll then find Ferrus just sitting around, talk to him, and them mess with throwing cannnoballs at him and blowing my whistle. I won't spoil it, but it's hilarious.
In SS, I usually clear a temple before I have a reson to wander around aimlessly, so I'll use this wacky new item I got to mess with th Sheikah Stones(again with the hilarity). I go to Skyloft and shoot pumpkins and pople.
I'll also shoot pumpkins in TP, but then I'm more prone to go into Catle Town and mess around in the market, goin back and forth between the apples that are evidently sweeter than each other. At night, I'll do the same with the men that are looking at each other. I'll also just go around and talk to everybody. Then I slip outside, go into wolf form, and freak everyone out. I swim around in both games, but it's way cooler in TP becuse Lake Hylia is deeper. For a thrill, I change clothes at the bottom and try to swim up, putting my Zora armor back on just before it's too late.
In PH, I'll shoot everything I see and go to a random island and dig holes. On the entire goram island. I filled my wallet like that one lazy day. I go outsdide halfway through temples and mess around with my new item. I annoy Linebeck. I fish for hours. I chase Jolene, get mad at her for being exacly the same as before, and crush her sorry washizaki. Yes, I know what a washizaki is.