A build may be manually triggered by right clicking on the build definition in the Team Explorer and selecting Queue New Build...
This will then present the Queue Build dialog for the build definition.
If available, you may modify the build defaults such as build agent, drop location and queue priority as well as passing command line arguments to the build agent. The position of the build in the queue will be calculated and displayed in the Position box. Note that when triggering a Team Foundation Server 2005 build, the build agent drop down, drop folder, queue priority drop down, position and MSBuild command-line arguments will be disabled.
Press Queue to start the build.