Contour shape and Line of Action in character development are important and literally can shape the attributes of the characters themselves.

You mentioned a bald military character? Try triangles or squares as a base shape. They are solid, authoritarian and have an air of command behind them.
Two thin kids? You can have a varied thin shapes, otherwise you risk running into same face syndrome.
Perfect example of great character redesigns: Ducktales (1989 vs 2018)
Original 1989 Triplet Designs: Same voices, same goals. They could literally be ONE character.

New 2018 Triplet Designs: Each one has a unique and individual design which can let the viewer know their own personalities.

Dewey is assertive and ready for action. Huey is confident and positive. Louie is smug and cocky. Each contributes their own goals and worth to the team, which the viewer can identify immediately from their new character designs.
You also need to think about how their design relates to their personality and movement.

Tom & Jerry have always been great analysis of character design in motion. Over exaggeration in comic action is important to keeping panels interesting as well as establishing how characters truly react in story situations.
Check out some YouTube videos regarding Character Design and implementation. I've found that Marc Brunet & Mitch Leeuwe have some good tutorials:
The key is to keep drawing and writing to improve! Its good to ask questions, but you also have to take some advice given from those in the community that are trying to help you!
Source: https://twitter.com/EtheringtonBros , https://twitter.com/artcycle , personal experience from being a teacher for over a decade.