You can guess some of the meaning of устаканились
у - prefix, often meaning away, or an aspect variation
стакан - glass
или - past tense, plural
сь - reflexive (acting on itself)
Looking at the word without knowing its meaning, you can say "The glass has taken away itself' The "y" prefix doesn't have an "away" meaning here (that happens with motion verbs, or the genative case), and you can't guess how a prefix changes a word exactly.
This can help with making an more accurate translation, though the word is idomatic enough that it is insufficient for a correct translation.
Does anyone know of a good book of Russian idioms?
QUOTE(slim @ Aug 16 2007, 09:14 AM)

I recognized the "stakan" part, but the rest didn't make much sense to me. I looked it up in my official dictionary and it didn't say squat about this word. So, I waited for my "unofficial" dictionary, a.k.a. my Russian wife to come home and asked her about it. She said she's never heard of it before and when I told her what the others on here said, she said "OK. I guess it can be used like this, but I've never heard this word before."
Seems that some Russian slang is regional.