Perfecting English skills is waste of time for the beginners. Once people clear the initial difficulty, however, they need to know details: especially, they need to know phrases they are using are commonly used or not. And commonly used English phrases by Japanese are often wrong partly because they are constructing English sentences in Japanese mind sets.
This does not mean they should brain wash themselves with Anglophone culture and custom. It just means people need to know commonly used phrases, and inventing phrases without knowing English in some details would cause confusion. Literal direct translation often makes wired English expression.
This problem is not specific to Japanese but to all the other non-native people. Or even Anglophone people often encounter difficulties as well if regional custom is different from their own. Obviously people cannot what I am writing here do not need to worry about this type of mistakes but people who are teaching English in any way should know this.
So what kind of errors do Japanese make? These days Japanese are writing English in blogs and twitters, we can see errors people often make.
attend to Osaka university to study=>attend Osaka university to study
my nickname was determinated.=>my nickname was determined.
Kids go university. Parents will go to the university to see their kids.
I’m a starman. ?? Are you alien? I do not get it.
to achieve deeper communication with people all over the world.= to communicate with people around the word. A complicated sentence does not make a better expression. Simple is best if you are not sure. Fewer words will make fewer possible errors.
I believe reading is important for enriching life.=>I believe reading can enrich our life.
「発音は完璧だけれど、語彙が少ない人や 語るべき内容がない人」はまったく尊敬されません –> No one respects fluent English speakers with little vocabulary and intellectual depth.
This is true, with a caveat: when it comes to a talk in a large scientific meeting where people’s brains are saturated with little concentration left, they usually just walk away from bad speakers unless they are famous enough for people to stay in a room for the sake of just being there. A bad speaker includes a native who is not good at giving a talk as well as incomprehensible speaker for various reasons. Keeping right balance is important after all.
More informally let think about why people talk to you in the first place. They want to exchange information: we can naively define that communication consists of three component:
information quality=signal content (speaker )* signal quantity (speaker) * ease of comprehension (listener)
communication value = your knowledge * your English skills * ease of understanding of your English
communication value (in general) = your knowledge * your communication skills * listeners desire to listen
Based on this, if your knowledge is close to zero then people have no point to talk to you. If your knowledge is substantial but your English skills are minimal then some people may want to talk to you but in this case, your listeners must decipher your sentences. We can come up with different scenario to maximize communication value. We can conclude that people should think about how to maximize the value of communication depending on the situation. (So we came up with very obvious conclusion.)
Other errors we make — the errors below are intentional, in case you do not notice.
1) We like cat and dog, though we do not eat them.
2) We like many atmospheres.
3) We do self-introduction instead of introducing ourselves.
4) We go to your place instead of coming to your place.
5) We say yes with a smile, when people ask if we mind they like to talk to us.
6) We like to talk about politics and general erection in public.
7) It is said that we Japanese write indirect sentences.
8) We wash us not our self.
9) We hate “the”s and “a”s: articles are evil.
10) We cannot use prepositions.
He is popular in people. => He is popular among people.
11) We cannot make sentences.
12) We just literally translation Japanese to English word by word, hoping that will do a trick.
Is your computer moving? => Is your computer running/working?
13) We cannot distinguish the subtle difference between can and do.
Could you see a lot of people? ==> Did you see a lot of people? is more natural. Do is sufficient when Japanese like to use can.
14) Many other English errors found in my blogs are likely to be typical Japanese English errors. But I do not think you will see many totally incomprehensible errors and if I see errors I can correct them.
15) If you own unique valuable concepts and ideas, people who need your information will guide you through and they extract information from your cryptic monosyllabic incomprehensible English, if they have time. Otherwise, they will let you improve your English at your own pace or they will be just nodding through your talk, dreaming about what they are going to eat for supper.

Nitpicking
@gkgk 中村岳
Snowing from the morning. I’ll go snowboarding tomorrow! #twinglish #eigodewa
=> Snowing this morning or Snowing since this morning is better.
He is the CEO of Rare Job, an online English conversation school. He can manage a company but not his English. This means he is busy running the company and Rare Job is just a school for conversation.