Xfire not only lets you join in on games your friends have already started, it also provides a server browser to help you find a place to play any of the games that support Xfire One Click Join. To get to the server browser, simply click the "Servers" tab in your Xfire client.
On the Servers tab, the "All" heading is full list of servers for the games you have installed on your machine. Double-click one of the game headings to open that game's list. Click the Ping header at the top of the list to sort the servers by ping. When you find a server you want to join, just click the join button.
If you select one of the game headers and open the Infoview pane, you are given a set of filters to help you narrow down the server list to a list that is more relevant. You can hide empty and full servers, query by game type, game options, or use game-specific tags to find particular servers.
The Recent Game Servers category will automatically populate with all the servers that Xfire has detected you playing in recently. If you come across a good server that you want to play on again, don't worry about writing down the IP address - Xfire will note it for you, and you can join in again anytime.
The favorites list allows you to specify certain servers you enjoy playing on. You can add any server on the servers tab to the list simply by clicking the "Add to Favorites" button at the bottom of the Xfire client. You can also add a custom server to the list by right-clicking the favorites header and selecting "Add Custom IP to favorites."
Friends' favorites provides a list of what servers your friends have marked as their favorites. It operates in the same was as the All servers header, but only shows servers your friends like. And if your friends like those servers, you might as well...
The LAN Servers section will scan your LAN for existing games, rather than using Xfire's master internet server list. You can hit up your local LAN event or PC cafe and quickly find out what people around you are playing, and then hop onto those servers.