How do Chinese judge the right sound quality (softness, awkwardness, respectfulness (面子), negativity)
Here I try to give some guidelines, not hard rules for sure.

Wrong Word Order

When you are not sure in what order to put elements in a sentence, stick to this:

Attributive + Subject + Time Adverbial + Place Adverbial + Manner Adverbial + Verb + Complements + Attributive + Objective.

For example: 新来的/那个/同学/昨天/在图书馆/高兴地/借/到了/那本/很有名的/小说。

新来的 － Attributive
那个 － Attributive
同学 － Subject
昨天 － Time Adverbial
在图书馆 － Place Adverbial
高兴地 － Manner Adverbial
借 － Verb
到了 － Result Complement
那本 － Attributive
很有名的 － Attributive
小说 － Object  

If you change the order of them, it is likely to make it sound awkward.

Incompleteness

Don't say 他在床上躺, instead say 他在床上躺着. 躺着 has the sense of completeness over just 躺.

Wrong Usage

Don't say 我病, instead say 我(生)病了.

Don't say 我很病, instead say 我病得(很)厉害.

Missing the 2nd part of a phrase pattern

There are a lot phrase patterns in Chinese made of paired words, like 一...就, 不是...而是, 即使...也. Sometimes the stuff going into between may be very long, so don't forget the 2nd part of those patterns.

So don't say the following sentences:

我一听到这个令人振奋的消息来了。 (Should say: 我 一 听到这个令人振奋的消息 就 来了)

迟到的人不是他我。 (Should say: 迟到的人 不是 他 而是 我)

即使明天下雨我去。(Should say: 即使 明天下雨我 也 去)

Wrong Tones

In one episode of 非诚勿扰, a Korean girl was asked by the host that where, if ever, on her body she got plastic surgery. She wanted to say 秘密 (secret) but she said 咪咪(a slang for breasts) which made the audience burst out laughing.