@achronic I have 2 tips that you might find helpful.
First tip (and most important) : be confident. Quickly drawn lines tend to be smoother. Imagine if you want to draw a circle. If you take it slowly it's probably going to look wrong. However if you draw it with a single quick line chances are it's going to look like a circle. If not, you'll certainly get it right after a few tries. So, whenever you want to draw something, don't hesitate and start wondering if the line you're about to draw is going to look right. Just draw it. Eventually by practising a lot you'll know exactly where and how to draw your lines so you will be really confident when doing it. I can see in my own drawings that the line quality is a lot better when i'm drawing something that i'm familiar with.
Second tip : Practise you line weight. In case you are not familiar, line weight means that the same line will be thicker or thinner in different areas. For example say you want to draw an arm. The side of the arm that is in shadow or further away from the light source can be drawn thicker than the side of the arm that faces the light or is closer to the light source. And there are more ways to use line weight. A lot of comic book artists tend to draw the shillouette of their characters with a thicker line in order to make them pop out of the background. If used right this teqnique will not only make your drawings a lot 'cleaner' and easier to read but it will also give them a lot of life.
i'd recomend studing black and white comics or watching some tutorials on this.
I'm also trying to get better at both those things so be sure to do further research if you're really interested in the topic. Nevertheless i hope this helped and thanks for the comment 
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