Hong Kong's main nightlife districts are compact and easy to navigate. Lan Kwai Fong in Central is a dense cluster of bars on a couple of uphill streets — lively after work and packed on Friday nights, heavy on expats and office workers. The area around Wyndham Street and SoHo (above Lan Kwai Fong, connected by the Central-Mid-Levels escalator) has a wider range of bars and restaurants, slightly less frenetic.
Wan Chai, east of Central, has a longer nightlife history — it was the city's bar and club district for decades and still has a lot of establishments along Lockhart and Jaffe Roads. The crowd is more mixed; some venues cater to tourists, others are neighbourhood pubs.
Tsim Sha Tsui in Kowloon has bars aimed primarily at tourists along Knutsford Terrace and Ashley Road, but the area has genuine character mixed in.
For a quieter drink, the hotel bars in the grand old properties are worth the price: the Felix Bar at the Peninsula Hotel has extraordinary harbour views, and the Long Bar at the InterContinental is one of the better waterfront spots.
Hong Kong's cha chaan teng (Cantonese tea restaurants) are cafes rather than bars — cheap, quick, and serving a distinctive menu of milk tea, toast with condensed milk, macaroni soup, and pineapple buns. They open early and close mid-afternoon. Every neighbourhood has at least one; they're an essential piece of Hong Kong food culture.