Visitors to Prague will have a lot of options when looking for ways to pass the time in the evening hours. The variety of options is growing, but it is still not a city that can match a Paris or a London. But that can be a good thing -- in terms of price, crowds, and more.
There are a number of sophisiticated cocktail bars in the center of Prague. Tretter's, near Old Town Square, has a classic atmosphere, with a well-trained and customer-friendly bar staff. Also in the area are Zapa Bar and Bugsy's. Behind the Tyn Church on Old Town Square, there is Tynska Bar and Books.
Close from the Old town square don't miss the Cilibar, (Take the street Melantrichova and turn first left. The Cili bar situated in Kozna 8) they are serving the best cocktails in Prague for the lowest prizes. A small, cosy, a little smoky but nice bar will capture you for hours. And you will taste the best Daiquiri ever.
If you want to mix some dancing with your drinking and eating, there is Solidni Nejistota, a few blocks behind the National Theater. There is also La Fabrique, near Wenceslas Square. For something even more Czech-oriented, try Meloun also near Wenceslas Square.
There are some serious discos in Prague. Radost FX, behind Wenceslas Square has many visiting star DJs for the dance floor downstairs. Upstairs, it is a hip lounge and vegetarian restaurant. Karlovy Lazne is a mega club near the Charles Bridge, with three different dance floors on different levels. There can be a long line here along the Vltava river in warmer months. On Wenceslas Square, there is an elevator entrance that will take you up to the club, Duplex. Mick Jagger had his 60th birthday party here while the Stones were touring.
Perhaps this sounds like a contradiction, but for a generally younger crowd, there is 80s and 90s night Fridays and Saturdays at Lucerna Music Club on Wenceslas Square. This is a fairly large club and it regularly fills to capacity. Another favorite of young people is M1 Secret Lounge on Masna, near Old Town Square. The crowd is generally a mix of well-off young Czechs and expat students.
For blues and/or jazz, some good performances can be caught at U Maleho Glena, near Malostranske Namesti. The performance area is very small with just a few tables. You might want to check the performance schedule on the Internet and book ahead if you can. The same goes for Ungelt Jazz and Blues club, behind the Tyn Church.
Other places that are good for hanging out and drinking great beer with your food are: Pivovarsky Dum on Jecna, near Wenceslas Square, U Vejvodu near Narodni Trida, and the historic 500 year-old brewery, U Fleku, near Karlovo Namesti and Narodni Trida. Waiters walk around with trays full of shots to offer to customers, but you should know they don't do it out of kindness. They will be on your bill later.
The side streets near Wenceslas Square are full of strip clubs. This is Prague's red light district. Pickpockets can be a problem in this area at night (often women who run up to groups of men asking for a hug, etc.) But it should be noted by all that pickpockets are a serious problem all over Prague, especially on public transport and crowd situations.
For very serious nightlifers, Adela Tours (http://www.adelatours.com) offers guided nightlife tours of Prague Discos, Pubs, and Jazz Clubs for couples, groups, or individuals. You or your group get your own Czech speaking guide for the evening. This is probably a great option for those traveling alone as well.
Travelers should change their money in the daytime through their hotel or a local bank and avoid the kiosks along Wenceslas Square at night because the commissions are outrageous.
Also remember that the underground metro closes at midnight, at weekends at 1am.