Rowan Atkinson once said he played Mr Bean by imagining what a 7 year old boy would do in a given situation (hence the nativity figures' encounter with a truck of sheep, a tyrannosaurus and a dalek).
Place one of your characters - or make up a new one - in one or all of the following scenarios and write what they do.
A waiting room.
A queue for the toilets.
A crowded bar.
What do they do? Where do they look? Do they speak to anyone around them? Do they fidget? Do they have any mannerisms or habits?
Better still, if you're in a room alone, or even if you're in company and just fancy adding a touch of eccentricity to proceedings, pretend you are that character. And do what they would do. Then write about it. Try using strong verbs rather than adverbs and stick to what they do, not why they do it.