I think which event happens is random, but the fact that an event happens is much less random than you think. I sometimes walk around doing nothing talking to people, and I get a m.o.m., dwarf, rick turpentine, sandwhich lady, or that pirate. That's once in three hours. If I am gaining a lot of exp in one skill they happen much more often. Autoers are usually gaining levels, and experience very quickly. If you went from 40 - 5* in one skill, one day, that's very good, but the exp at that level isn't as large or as fast as a higher level autoer. With prayer and cooking I've notice there are some patterns, just check it out.