どう言い表したらよいか
「敬語や丁寧語を使えるか使えないかということで、その人の人格が判断される」と日本語の先生に言われたことがあります。私の日本語はちゅうきゅうなので、どう言い表したらよいかわからない時が多い(ん)です。なお、最大の心配は他人に下品とか無礼にみられることです。無礼な態度を取っていなくても、私は、間違った日本語のせいで、礼儀正しくない人にみられたら、一番恥ずかしいと思います。

My correction is almost same as Yoko san. 
My opinion about honorific (or honorific and polite Japanese language structures) is that foreigners needn't so much worry about it, which might be contrary to the opinion of your teacher. Because it isn't so easy to use it perfectly even for Japanese. And we can at least understand the intention that foreigners are trying to use such honorific even it contains anything incorrect in use.
This is the information for your study. The very basic idea of honorific is to upgrade others and downgrade yourself. You can imagine others will be glad by doing this :) Typically for a very common expression する(do), you can use されます (or なさいます) when talking about others, and you can simply use します (or いたします) when talking about yourself. By only full use of just these several words, I think it looks to be so-so for speaking honorific :)

どう言ってい表してよいか

日本人にとっても、尊敬語、謙譲語の区別が難しいときがあります。ですので、外国の方が間違えるのは当然だと思います。私は全く気になりませんよ。

A Japanese teacher once said that my ability to use honorific and polite Japanese language structures would determine how others judged my character. My Japanese language level is intermediate so of course, there are often times where I don't know how to express what I want to say. Moreover, the biggest worry I have is that others will think I am being rude or unpleasant. Although I don't have a rude attitude, I think the most embarrassing thing for me is if people think I am being rude due to my incorrect use of Japanese.