I've never been a fan of the third-person omniscient, where the reader observes every thought of every character. It's unnatural.
I prefer an observant first-person or a detached third-person. I like to see emotion and motivation through the movements of characters. The little things they do or don't do. How they react. Show me, don't tell me, what they think.
I'm a people watcher, professionally and personally.
I love to sit on a park bench, watch the world go by and take guesses at what people will do. Will they greet with a kiss or a handshake? Will he turn to look at that woman's ass after she passes?
As a bartender, people watching is essential to customer service. Do you look like you're in a hurry or are you finally taking it slow after a hard day's work? You said your meal was fine, but are you pushing it around the plate and just too polite to say you don't like it?
And of course: how drunk is that guy?
Good writing is about delivering the little details of body language that reveal character.
Keep your eyes open.