What makes a character three-dimensional?

1) KNOW YOUR CHARACTER.

2) Description,
a) keep a list or even a notebook. It’s often best to use composites of real people you know.
b) Give details sparingly, only those that are relevant, avoid ‘description dumps’
c) Beware of brand names, they date you and your writing. Better to describe the object and or its significance.
d) Use many senses, visual, auditory, tactile, taste
e) Remember body language, surroundings that can tell us about a person
f) Avoid self description , and of course clichés

3) Dialogue
a. Word choice and grammar, In real life they are seldom precise or eloquent, but that may vary between characters.
b. Use dialect slang and professional jargon sparingly if at all. Use enough to establish an accent, social class, or expertise but then fade back into something more readable.
c. Use ‘said’ but not every time, avoid adverbial tags
d. Use dialogue to reveal relationships and create tension before and after actions.
e. DIFFERENT CHARACTERS SPEAK DIFFERENTLY

4) Backstory
a) Thoughts, reasons, and deeds arise from the characters history
b) Might be handy to keep a chronological list of when important things happened to your character.
c) motivation, how has his/her history led to present thoughts and deeds
d) don’t be overly specific lead the reader there but don’t force feed them.
e) don’t give all the backstory at once, feed it in as it becomes important and use both dialog and expositional description to do the job. Be sneaky, no one wants to read through three paragraphs of a characters ancient history unless it’s REAL interesting, so if it’s not break it up and slip in as needed.
So having absorbed all that, lets run this story through the mill once more . This time building up the tension until those shiny characters can’t take it any more. When you are done we the readers will understand the motives of the protagonists and will have chosen sides based on your descriptions. Give us a reason for cheering him (or her) on. best of luck
Mad Lews