When should I use "in" or "on"?

I'm not surprised you are getting different answers to some of these, because this is just the sort of thing that tends to vary quite a bit by region. For instance, as someone raised in California, I say that I am "in line", meaning I am waiting in line. Others (I believe this is a northeastern thing, but I may be wrong) say "on line", which has always sounded very odd to me.

One of the reasons you get this kind of variation, I'm afraid, is precisely because there are no consistent rules. Or rather, I should say, that there are many cases where one or the other could be used depending on how you conceptualize the situation, and these are just conventional. For instance, in your bus example: on the one had you are definitely inside the bus, but on the other you have boarded and stepped onto (not on top of) the bus, so you can see how the latter may have come about.

For my dialect, it's: "good luck on" and "on the list".

Though I think both variants sound fine too.