I'm the type of person who enjoys getting to know people. I don't mean what's your favorite color or do you like your eggs scrambled or fried getting to know. I mean, I want to know what's in your heart and on your mind. What do you ponder when no one else is around, what wakes you up at night and drives you out of bed in the morning?
Approaching new characters from a place of nuanced curiosity creates a connection for the reader that (hopefully) makes you want to travel with them on their journey, route for them to succeed or take pleasure when a villain gets a mud pie right in the puss. I've found that if I don't fall in some degree of love with a new character after a page or two, it's best to either kill them off quickly or put them in the dust bin forever. Basically, if I'm bored with them, there's zero chance you'll find them exciting.
On the other hand, people are rarely boring and even boring can be written to be exciting. Also, having a virtual people factory at your fingertips can be intoxicating. You want that guy to wear a monocle and walk with a limp, go ahead. You want your heroine to use dirty jokes to cover up a secret from her past or bring in someone who sweats on command when he hears the word "chocolate"? Feel free, there are no rules other than I need to care about the person/animal/mineral enough to stick with them. That being said, does your new character really need that monocle? The answer is--it depends.
Tell me who you are and why I should care and I'll follow you anywhere. Give me a one dimensional cutout of a character and I'll forget about them forever.