Edited at 5/16. Corrections and rewordings (Thanks, Peter)

Hi everyone. I am learning English on this site and I also do some corrections to essays of people who are learning Japanese.
I have recently dived into the site and devoted myself to correcting their wrong sentences. Through this experience, now I have noticed a single key point for people practicing Japanese, so that they may come to  improve their writing on their own. 
I will describe to you this secret to write more authentic-sounding Japanese here.

MUST use the comma「、」 where you can use it
Learners tend to combine their phrases into long, but intelligible sentences. Those long sentences are susceptible to incorrectness. Because when you make a long phrase, you have to pay more attention to various rules and the pragmatic view of co-occurrence which words would be appropriate with the word. What I mean by "phrase" here is each part of a sentence separated from other parts by comma.

For example, think about this.

- 帰り道で母は晩ごはんってうどんにしようかと言いました。

This sentence is not explicitly wrong, but somewhat awkward to me. Because this part 「晩ごはんってうどんにしようか」 may be wrong in writing, but acceptable in speaking. At least, we must separate the part that is  direct discourse from other parts like this. 

- 帰り道で母は、晩ごはんってうどんにしようか、と言いました。

You can remember this replacement technique as a rule for direct quote separation, but I propose that you remember this as a more general rule, which I call "the distinctive comma". "Distinctive" means that if you can insert the comma into any parting of words, the distinctive comma must be inserted there like this. 

- 帰り道で、母は、晩ごはんって、うどんにしようか、と言いました。

And then, you need to check which parts are strongly connected. If you find some connected groups of words, assemble them.

- connectivity groups:
帰り道で、
晩ごはんって、うどんにしようか
母は、と言いました。

- rearrangement:
帰り道で、晩ごはんって、うどんにしようかと、母は言いました。

Actually, you can improve the sentence a bit more here. You might notice that it would be more natural if you would say it like this.

- 晩ごはんって、うどんにしようかと、帰り道で、母が言いました。

This is because if groups more strongly connected by their meanings are placed closer together, listner can get the sentence meaning more easily. 

I think also the particles, such as "は", "が",  is the hardest obstacle to learners, and this technique would help them to determine the particles properly, because they can find the phrases are clearly related after the rearrangement of words.

I hope you'll actually try this. Thanks for your reading.