1. Referring to oneself as -san.
This is a simple but common mistake probably due to equating –san with Mr/Mrs. You don’t use –san when talking about yourself, only when talking about others.
2. Using wo instead of ni with certain verbs.
Most verbs take wo so this is an easy one to get wrong.
E.g. Noru takes ni not wo. Densha ni noru (to get on a train).
3. Trying to learn kanji and kana by copying them out endlessly.
Use a radical based mnemonic method like Heisig’s.
4. Confusing long and short vowel sounds.
Vowel length is very important to the Japanese. It could be compared to the difference between l and r in English.
5. Saying gairaigo (English loan words) in English instead of Japanese.
The katakana pronunciation of an English word is often markedly different to the English pronunciation which in many cases will not be understood, especially by older people.
E.g. Australia should be pronounced Osutoraria in Japanese.
6. Forgetting the ten ten mark when writing kana. This is very easy to do and completely changes the character.
You just have to be careful when writing by hand!
7. Not knowing the number irregularities with time and dates.
4 o’clock is yoji, not yonji.
The 1st to 10th dates of each month are irregular and have to be learnt as is the 20th.
8. Confusing the Japanese “come closer” gesture with the English “go away” gesture.
When a Japanese person wants another Japanese person to approach, they will gesture palm down and wave their fingers. This looks very like the “Shoo!” gesture an English speaker might make.
9. Trying to translate English to Japanese word for word.
This is generally not an effective strategy. Don’t get too hung up on the words you want to say but rather concentrate on the meaning of what you want to say.
10. Pausing in or emphasising the wrong part of the sentence.
Beginner Japanese speakers should speak as flatly as possible and use the particles as pause indicators (pause after particles).