pacman

Here are a list of useful commands to be used with pacman.
pacman may require some specific settings if your environment is behind a proxy, so you should have a look here.

Update and install the list of package.
pacman -Suy

Perform a full upgrade, is necessary if some libraries are missing to recompile systemt properly.
pacman -Syyu

Install a new package.
pacman -S $PACKAGE

Remove a package.
pacman -R $PACKAGE

Remove a package and its dependent packages.
pacman -Rs $PACKAGE

Look in package database for packages based on given keyword.
pacman -Ss $KEYWORD

List of packages installed as dependencies but not used anymore.
pacman -Qdt

List of packages explicitely installed, and not needed by other packages.
pacman -Qet

List of packages with given keyword.
pacman -Q | grep $KEYWORD

List of files installed with package.
pacman -Ql $PACKAGE