wow emily you might be like me...scary.
tricks? none. countless corrections? yes. hours of embarrassment? yes. making it any simpler? no.
but at least you're struggling with the same problem as most of us: the native system throws us for a loop. Just when I get comfortable in the sino system, I find out I should have used the native system instead. opps.
my tutor explains it like this: always assume you use the sino numbers. then, there are exceptions. hours of the day, counting small things like bottles, pieces of candy, people, and age (mostly). I say mostly because, like Keith points out, some Koreans don't know/use the native system past common cumbers (usually past 30 or 40 or so). Even then, I'm happy to hear that even native speakers prefer the sino system but obviously cannot imagine 한국말 without the native system.
So, matthew's tip of the day: when in doubt, use the sino system. Just remember the exceptions.
as far as time, I picked this up out of force - my tutor makes me use it even if I don't speak any other Korean - I
have to use Korean with time of day. Even still, like you, in any language, I struggle with time (and numbers in general). But you personally have such an outgoing personality that for it should take less time to get it down. For me, I started with flash cards...
Okay, now as far as the grouping problem with big numbers, think in terms of modifying/multiplying a counting system - not using a system itself. In English, we can just always assume a logical progression: ones, tens, hundreds, thousands, ten thousands, hundred thousands, etc. But with Korean, it works more like ones, tens, hundreds, thousands, ten thousands, ten times ten thousands, etc
http://www.langintro.com/kintro/numbers/sinokor.htm
keep'em coming. what does everyone else do with numbers to help them?
for confessions of a numerically challenged Korean language learner, check out:
http://blogs.koreanclass101.com/blog/20 ... -no-sense/