Funnily enough, characters are surprisingly vital to a story. I used to think that the more characters the better, where I could flex my creative muscles and have a huge assortment of quirky, stereotypical and (most importantly) different people in my stories. While this might work for perhaps a game of Dungeons and Dragons, where doing a funny voice and a weird talent will get a few laughs but soon the character is forgotten about and never mentioned again. I don't want this in my stories. I want everyone who should be memorable to be memorable. With our current novel, we kept the character count relatively low as we really wanted each one to be fleshed out as much as possible. We wanted to be able to tell you every detail about how they would talk, react to any situation, what they like, what they dislike, who do they know, their families etc. This might all seem obvious but, at least for me, having so much detail on our characters made writing about them so much easier. How would X react if Y told them this? Of course X would do this, because of Z. I would recommend filling out a character sheet for at least your main characters if you plan on writing a novel of some sort (for example: https://www.epiguide.com/ep101/writing/charchart.html). You can do as little or as much as you want, just the process of doing it can give you a clearer picture in your head, as well as a handy reference guide for even simple things like description. It took me far too long to remember what colour my main character's hair was until I wrote one of these. My original problem, which I would like to hope is now remedied, is that I would have a character that is effectively just a quirk. They would have one thing about them that would just BE that character (aka. he's always nervous, she's a barbarian, he's a blind pirate etc). This did not lead to very interesting characters, with very cliched moments and an overall boring read. Our current novel ending up cutting several characters like this, including a grizzled detective, a fast-talking salesman and a flatmate character so boring I can't even remember what they were like at all. All necessary cuts that have made the story so much better. But this still left the remainder of our cast, and I knew I had to adapt if I wanted to improve the story. What makes a person a person? How about I just base my character around an actual person? This is often my first step when coming up with a character now, as a real-life person (especially someone you know well), already has a huge amount of details to them. You know how they talk, react, what they love and hate so you can gain a very clear understanding of the (what I would say is) the base of the character. About 90% of the characters in our current novel were based on people we knew; flatmates, family members, friends and even ourselves (and no this is not a self-insert fanfic, though it nearly could have been if we didn't progress from this point).
This is where the next step came in. We took the person we knew, and altered them to the situation, tweaking parts of their personalities to make them a new person. This is quite difficult to explain, and I do feel I perhaps have wasted some of your time if you were reading this to learn anything.
Most likely I will do a secondary post regarding the next step in character development for me (have to get those view counts up somehow),