It really depends where you're going. Fashionbeans did a couple of really good articles last year on what to wear when going out to different types of places, like the pub, to a smart bar, or to go clubbing:
How To Look Good – In An Upmarket Bar Or Club | FashionBeans
How To Look Good – Down The Pub | FashionBeans
All the advice you need should be in those articles to be honest.