Want To Dress Casual And Look Great? Casual Dress Tips For All Occassions When Should You Dress Casual? You can choose a casual outfit to run errands or relax with friends at a summer BBQ. If you know that you’re going to be busy all day, you should plan to wear something comfortable. Trousers or shorts are a great option as they’re easy to run around in. Simple shirts or t-shirts and jackets such as bombers pair nicely with your favourite pants. Sneakers and slip on kicks are a good choice for footwear.