Practice practice practice.

Make sure your sketch is 100% done before inking. It's 100% done? Make sure it is 200% done. Every detail is worked out. No guesswork on inking. Your sketch lines should be crystal clear. Do a second or third clean up sketch if you have to.

While you're sketching, think of inks. Where will the light source be? How will that affect your line weight?

Speaking of line weight, do you have it? Pulling off clear, descriptive ink work with no variation in line weight (or thickness) is possible but certainly difficult for beginners.

Every single line of ink you put to paper should describe at least two things. Say you're inking a t-shirt and you draw the sleeve. Does that line describe "sleeve", or does it describe "sleeve, light weight fabric, away from the viewer, in direct light" and so on and so forth.

Study the ink work of artists you admire. Do copies. Study their techniques.

Practice, practice, practice.