Most Chinese educated Malaysians never have problems with kanji, maybe just experience  a bit of cognitive dissonance because some 10 to 20% having slightly different meaning. But it will not be of great help in passing JLPT until at least N3 or above. Their biggest problems have always been listening and speaking because many are passive learners who don't speak much in the classroom

It's 4 o'clock in the morning. I can't sleep, so I'll write something quite long. Hopefully it will be useful

From the posts I've read, most people learn Japanese from Anime. Although it's a source to pickup some Japanese, I would rank it somewhere near the bottom when it comes to picking up Japanese by listening. My list would be:

1. Variety shows
2. Podcasts
3. Documentaries/TV news
4. Doramas
5. Audio books/radio news
6. Anime
[unranked] songs
I'll go over them one by one, starting from the bottom.

Songs
Depending on your level, songs can be a very good or bad way to learn Japanese. Translations of songs are normally done verse by verse or 2 lines at a time rather than line by line. If you're a beginner, looking at the translation and trying to match the english phrases to the japanese phrases will be confusing and frustrating. Not to mention you'll probably end up matching the wrong phrases. If your Japanese is decent, songs can be a great way to expand your vocabulary, improve listening and expose you to creative writing in Japanese.

Anime
Before you fanboys get mad at me, learning Japanese by watching anime does expose you to the language. And if you learn by doing something you enjoy, you're more likely to stick to it. So why do I rank anime so low? For one, the Japanese you listen to in anime isn't the same as the one you'll encounter in real life. You don't need to know 10 different ways to say "I'm going to kill you" or words like テメエ(you muthafxxxxr!) unless you plan to go to Japan and be a delinquent. Knowing 海賊王に俺はなる (I'm going to become the pirate king) won't impress the girls either.

Audio books/radio news
This is a great way to improve your listening skills. The narration is done by professionals with very clear pronunciation. Here are some free audio books with text http://how-to-learn-any-language.com/forum...6241&PN=1&TPN=1

Doramas
The same benefits of audio books but with visuals. Because you can 'watch' it, you'll be able to understand better what is being said. There are also other benefits such as you can read stuff like road signs, shop signs, food packages or whatever pops up on the screen in the dorama, this helps with your reading and vocabulary. Not to mention you can gawk at your favourite actors/actresses. You'll also be able to learn a lot about Japanese culture and their way of life. Doramas have an advantage over anime in the sense that the language used in doramas are more similar to the one you'll encounter in real life.

Documentaries/TV news
Same benefits with audiobooks + doramas. Narration is done by professionals and you can actually watch it, rather than just listen. They cover different events happening in different areas and sometimes have interviews with different people. So you can listen to how different people from different areas with different social status talk. But most importantly, you get to listen to people talking naturally,which is the very reason I put podcasts and variety shows high on the list.

Podcasts
The keyword here is unscripted, natural speech. Something that documentaries have little of and the previous methods have none of. By podcasts, I don't mean a person reading off a script, that would be categorized under audio books. What I mean by podcasts is people talking to each other just as they would in real life. They talk at a natural speed, using regular words they would use everyday and their pronunciation is similar to the average Joe (or Takeshi) Podcasts can range from a wide range of topics from science, to video games, to simple ones designed for beginner Japanese learners. The weirdest one I've listened to was from TBS Radio where 3 guys talking about masturbation

Personally, the best thing I've done to improve my Japanese is listening to podcasts on the bus on my way to work everyday.  Within a few months, I went from being able to only say 私は。。。です or 私は。。。をします to having a real conversation with my Japanese friend when she visited. By real conversation I don't mean just お元気ですか？I mean asking about her family, the situation in Japan etc (it was almost a year since the tsunami) Obviously I did make some mistakes but it was a massive improvement from my pre-podcast days.

Variety shows
The benefits of podcast + visuals. Japanese variety shows are the best in the world. They can make you laugh, they can make you cry, and they can make you go "WTF just happened?" Obviously with visuals, you better understand what's going on. Just like podcasts, they speak naturally, and unscripted (to an extent) Plus, they have text that appear on the screen. So if they're talking too fast and you can't hear what they're saying, you can simply read the text. It's a great way to improve you listening and increase your vocabulary while enjoying yourself.

If you're into idols, there are shows like AKBingo(AKB48), Idoling!!!(Idoling!!!) and Nozibingo(Nogizaka46). If you're into pretty boys, you can watch "vs Arashi"
on 8TV every Sunday. If you want to have a good laugh, you can watch Gaki no Tsukai (ガキの使い) or Lincoln(リンカーン) If you want to watch awesome athletes competing against each other, there are shows like "Sasuke" and "Pro Sportsman No1"(最強の男は誰だ!壮絶筋肉バトル!!スポーツマンNo.1決定戦) There's always a show that suits you.
Yes it's used for words borrowed from from foreign languages it's also used for Japanese words as well. Some other uses of katakana

1. words someone just blurts out in anger, surprise, wonder etc. eg:マジ? (really?) ワァ！(Waa! [in amazement]) バカ!you all probably know what this means.

2. Onomatopoeia. ニャンニャン、ワンワン、ブーブー (meow, woof, oink respectively) other sounds such as ガオ(roar) ピカピカ(sparkle. How Pikachu got it's name)ワクワク(excitement)

3. Replacement for normal words that have difficult kanji.ゴミ(塵,garbage) アリ(蟻,ant) ガン(癌,cancer)

4. Transliteration for company names. セイコー(From 精工舎) トヨタ(豊田)

5. Words that have their own kanji, but borrowed from Chinese words. ウーロン茶 (Oolong tea.烏龍茶) ラーメン(ramen.拉麺)

4. Slang/accent. テメエ(you, [gangster]) コイツ(this guy, [gangster]) コラ(something a gangster would say at the end of sentences to his victim) ボブトモ-シマス。ヨロシクオネガイシマス (I'm Bob. Yoroshiku onegaishimasu. Written in katakana to indicate that he's a gaijin and speaks with a foreign accent)

5. Technical/Scientific terms. In a technical environment, 'people' would be written as ヒト rather than 人