I like Hemingway's edicts about "Write what you know" and "Write people, not characters". It's the "Write what you know" that first got me into writing history. And "Write people, not characters" is absolutely true: who would want to read a book about, say, a noble communist? Only dyed-in-the-wool hard-core communists. Who would want to read about crooked bankers or greedy politicians? Only people who hate bankers and/or politicians.
OK, bad example. But the point stands: give your characters more than one defining feature. If they're (largely) noble, give them a not-so-noble feature. If they're (largely) villainous, give them a redeeming feature. Otherwise, they're boring.
I've read two anecdotes about Hemingway that I really liked, and I'd love to share them.
- F. Scott Fitzgerald remarked to Hemingway that the rich "are not as we are."
"No," replied Hemingway, unimpressed. "They have more money."
- In a Sun Valley restaurant, a stranger asked Hemingway for his autograph. "Thanks, Mr. Hemingway," the pleased visitor said cheerfully when he got the signature.
He passed the table again and said, "Hello, Mr. Hemingway."
Intoxicated by being so near the great man, the stranger permitted himself another walk past, this time calling out, "Hi, Ernest!"
Made further giddy by Hemingway's acknowledging nod, the man made one final pass, this time calling, "Hello, Papa!"
Hemingway lowered his beard and raised his arms. "Hellooo!" he roared. "And goodbyyyye!"