I usually just talk to friends in my clan and bankstand or afk fish and watch tv or something. I can't really talk to random people because most of the people I meet in my homeworld are all trolls and whatnot but that's Runescape for you haha.
Honestly, I'm not a big fan of wasting time on RuneScape.
I'll try to train a skill or go PvM'ing.
Those are all still great opportunities to talk to people and make new friends as well, so it's never too boring
Honestly I've always liked just going to the duel arena/clan wars to mess around for a while. Love testing out different gear and setups there. Sometimes I'll funbrid/dh people in the duel arena/clan wars also with pking setups so I don't have to re-gear.
Another pretty fun thing to do is gear up and do a few barrows trips, always pretty entertaining to me.
Always could give gwd a try/something like dk's just for fun.