Here are a few command line tools that will help you estimate your system usage and performance.
There is a lot more information on this in the man pages so take a look there also. If you dont know your average system load you will not be able to determine if the load is in a peaking state or if the host is able to handle more load.
Note that some commands might require installation of a few packages.

Below gives a nice simple performance view of a HDU. Ofcourse running...

Sometimes it can be quite a challenge to find out what hardware you have but it is actually quite easy.
Here are a few commands and some sample output for you.

USB devices are usually easy to identify because you can just pick them up and look at them.
Below will help you out with the few that just say NoName on it. Often those noname ones are the same as the named ones just with another wrapping. Below display a list of detected USB devices.

# lsusb
Bus...

If you want to watch a log file and have it update when ever new content is added the "tail" command is an easy on-the-fly tool to use.
Ofcourse for long term use other implementations of log file analyzers or syslog services would be better.
Here is a short example and some sample output showing a failed root login attempt.

# tail -n 20 -f -s 5 /var/log/auth.log
Feb 17 04:11:09 testbox login[4822]: pam_unix(login:auth): authentication failure; logname=LOGIN...

Sometimes it comes in handy to know what libraries and what versions of those libraries some software is depending on.
This is quite easy and is done with the "ldd" command.

Here are the dependencies that the "ls" command has. Remark that you have to use the absolute path as ldd does not support the use of the search path stated in the environment variable PATH.

# ldd /bin/ls
linux-gate.so.1 => (0xb7fd4000)
librt.so.1 => /lib/i686/cmov/librt.so.1...