If you're writing a novel or a screenplay, think about the characters that have stuck in your mind from the books you've read and the movies you've seen. Would you say they are average people? Most likely, no. Probably they're bigger than life. The ones I think of include the Godfather, Hannibal Lector, and Ellen Ripley (Aliens).
Obviously this is influenced by the kind of story you are writing, but at the idea stage it’s good to make your characters big. If someone is stingy, make them REALLY stingy.
A great example from real life is Hetty Green, a woman who came to be called the Witch of Wall Street. She was born in 1834. When her father died she inherited $7.5 million (equivalent to about $110 million today). She made her fiancé sign a prenup contract renouncing all rights to her money.
When her Aunt left $2 million to charity, Hetty challenged it and produced a will that left all the money to her. The courts judged it to be a forgery.
Hetty Green developed an investment strategy that made her another million dollars one year but she remained an outrageous miser. She never used hot water or heating. She did her business at the offices of the bank she used because she didn’t want to pay to rent an office. When her young son Ned broke his leg she tried to get him treated at a clinic for the poor. The people there recognized her and chased her out.
Her son survived but eventually became as big a spendthrift as his mother was a miser. One of his prize possessions was a diamnd-encrusted chamberpot.
Of course you don’t want to make your characters grotesques, but it’s easier to go big with them at the start and then pull back, than it is to make them more interesting after you’ve drawn them as boring.
(Do you want to know how Dickens, Austen, Hemingway and many other great authors created their memorable characters? You'll find the answer in my book, "Your Creative Writing Masterclass." It's published by Nicholas Brealey and available from Amazon or your other favorite bookseller.)