1) When you see 止める how do you tell if it's 「やめる」「とめる」? Similarly, when is 少女　pronounced 「しょうじょ」 and when is it 「おとめ」? And 一昨年: 「おととし」vs 「いっさくねん」, 空く：「あく」vs「すく」, etc. I've run into a lot of compounds that have the same kanji/meaning, but different readings, so how is one to differentiate among them?

2) Is there any difference in meaning between 追う and 追い掛ける? They have the same definition, but does the addition of 掛ける add some extra meaning (similar to how あげる/くれる function)?

3) I haven't done too much listening, but how can you distinguish between words that sound very similar: ex. 振動「しんどう」 vs 震度「しんど」in conversation?

4) Also on the topic of listening, words that are pronounced the same but have different meanings: ex. 「かく」is 書く or 欠く or 描く ?

Kuzunoha13 Wrote:1) When you see 止める how do you tell if it's 「やめる」「とめる」?...空く：「あく」vs「すく」

In these cases the two different readings represent two different meanings. Context will usually be enough to tell which one is needed in a particular sentence.

Kuzunoha13 Wrote:Similarly, when is 少女　pronounced 「しょうじょ」 and when is it 「おとめ」?

おとめ is an extremely rare reading for 少女; it's far more common for that word to be written as 乙女. Don't worry too much about 少女, just assume it's しょうじょ unless the furigana says otherwise.

Kuzunoha13 Wrote:And 一昨年: 「おととし」vs 「いっさくねん」

The basic meaning is the same, it's just that the latter is a reading used in more formal contexts.

Kuzunoha13 Wrote:2) Is there any difference in meaning between 追う and 追い掛ける? They have the same definition, but does the addition of 掛ける add some extra meaning (similar to how あげる/くれる function)?

In the dictionary I'm looking at (i.e. Rikaisama) they don't actually have the same definition. Or rather, the definitions of 追い掛ける are a subset of possible definitions of 追う. I don't think 掛ける is a productive auxiliary verb in modern Japanese in the same way あげる and くれる are, but I'm not entirely sure.

Kuzunoha13 Wrote:3) I haven't done too much listening, but how can you distinguish between words that sound very similar: ex. 振動「しんどう」 vs 震度「しんど」in conversation?

I think you just answered your own question. If long vowels don't exist in your first language like they don't exist in mine (aside from a marginal lengthening of stressed vowels), you should get used to them by listening a lot. One activity that helped me with this particular feature was listening to songs while reading the lyrics. Unlike many European languages that have vowel length distinctions, in Japanese the long vowels usually take up two beats in songs and poetry, while the short ones take up one. This really helped hammer the distinction into my head.

Kuzunoha13 Wrote:4) Also on the topic of listening, words that are pronounced the same but have different meanings: ex. 「かく」is 書く or 欠く or 描く ?

Again, context should be enough. Although, in this particular case I could nitpick by pointing out that 欠く isn't pronounced the same as the other two in standard Japanese. There is a difference in pitch accents - 欠く is accentless, while 書く* and 描く* have the accent on the first mora (and here is how their accents change in conjugated forms). Whether or not pitch accent is something actually worth learning about is a rather controversial topic, so it's probably better not to go into more detail about it here.

*As an aside, I suspect that these two, and possibly also 掻く, were originally essentially the same word, and only started to be distinguished in writing because they were different words in Chinese.

Edit: expanded the answers to questions 3 and 4 a bit.

1) For 止める, see http://forum.koohii.com/showthread.php?p...#pid201283

vonPeterhof Wrote:I don't think 掛ける is a productive auxiliary verb in modern Japanese in the same way あげる and くれる are, but I'm not entirely sure.

It is, though in a fairly different way. I'd rather compare it to 込む, 出す, etc.
1. To ~ at someone
2. To start ~ing
3. To be about to ~
Also, "to be in the middle of doing ~" (used when ~ gets interrupted partway through):

その本を手にとって 2, 3 ページ読みかけたときに客が来た.　I started reading the book and had read only a couple pages when a visitor came. (example sentence from 研究社 新和英大辞典)

Thanks for the detailed replies! I'll probably have to add more info to my cards when they come up again.