Meanings and usage of words change over time. Those prefixes are very old, so it often happens that the word with and the word without the prefix slowly changed meaning, and one started to get used in one kind of situations and one in the other. So it's best to just treat them as different words, and try to get a "feel" for when and how they are used. One method that helps is to look up example sentences. Another method is "double lookup", you lookup the English/Chinese meanings for the German word. Pons is also useful, because it puts different meanings and usages into different categories: http://de.pons.com/%C3%BCbersetzung?q=heimisch&l;=deen∈=&lf;=de http://de.pons.com/%C3%BCbersetzung?q=einheimisch&l;=deen∈=&lf;=de You can see that the first has an additional meaning "in etwas heimisch sein", "sich heimisch fühlen in". That said, if you just want to guess the meaning of a word, there's some rules: directional prefixes (auf, aus, hinauf, hinein, hinaus, ...) are often straightforward (gehen -> hineingehen, hinausgehen) even if the verb is sometimes only used figuratively today (gehen -> eingehen, ausgehen), and the Duden has some explanations for http://www.duden.de/rechtschreibung/ent__befreien_von http://www.duden.de/rechtschreibung/be_ http://www.duden.de/rechtschreibung/er_ "Ge-" is in most cases a passivish sort of prefix.

As far as I know there isn't any rule, it just evolved that way. Some prefixes can completely change the meaning of the word while others dont affect the meaning at all. Heimisch can also have different meanings from native (like einheimisch) to homely, familiar depending on context. Usually you can use them interchangably if you look them up on the dictionary or confirm with example sentences. I guess this is something you'll get used to once you are surrounded by German every day, sorry I cant offer more advice on that.