Linux.com's Gary Sims lists various tools that you may use to monitor and manage your system processes. Budding system administrators should know these tools by heart. :)
This powerful feature of being able to start-restart-kill system processes on its own without reboots is one of the strengths of Linux (and other Unix-based systems). Make sure that you also know how to kill X11 and drop to the console so you can continue managing your system without unnecessary reboot. Mind you, most stalled applications and services can be restarted without rendering your system useless for a couple of minutes whilst it reboots.