same with german. My rule of thumb is, if it doesn't express a physical motion, assume u have to learn it as a new verb entirely.
What do you mean by that?
Some funny examples:
megpatkolni = to put horseshoes on the horse
elpatkolni = to pass away (slang: to kick the bucket)
csinálni = to do, to make
becsinálni = to mess someone's pants
felcsinálni = to knock someone up
kicsinálni = to wreck someone, or kill someone
While, with verbs of motion:
menni = to go
elmenni = to go away
kimenni = to go out
There are quite a few exceptions, of course (e.g. összemenni = to shrink), but this rule is useful for a start.
And by the way, I think the problem both Gothwolf and I had with the verbal prefixes, was how to know when it should be a part of the verb or not. At least that was my problem :P
I don't think there's a rule for that.
But that's a problem even in English, sometimes. For ex.: Pull your trousers up! (Not "Pull up your trousers".)