Start with htop. You can get that package from apt in a debian-based distro: `sudo apt-get install htop strace`. When you launch htop, you will see a list of a

Start with htop. You can get that package from apt in a debian-based distro: `sudo apt-get install htop strace`. When you launch htop, you will see a list of all your running procs. If you select a proc with the arrow keys, you can hit "s" to start a strace and then hit f4 to follow the strace as it dishes output. This won't work for all procs, you will need root to strace certain procs. This is a good place to start as it's visual and easy to follow. Later you can start traces from the shell with proc IDs and even get system call info from GDB.