In many places in the world, you can just head anywhere that sells beer and buy it. In Northern America, brew pubs and micro-breweries are the best hang outs to enjoy freshly brewed, greatly crafted beer. However, they are not found everywhere, yet.
A lot of restaurants and bars are starting to sell high quality beers in bottles and on tap. If you want to drink a great beer, never ask for an "import!" Today, the market can make you very disappointed while missing a really awesome domestic. Always ask for a beer list. It's not all the time that the servers are educated when it comes to beer lore and might misinterpret what you want in a good beer.
Plenty of liquor stores offer an amazing selection of bottled beers. Major groceries are also starting to carry popular selections.