See Arch Linux general recommendations for complete details.
About this document:
Won't have all the commands from the Arch Linux general recommendations, only the most interesting to me, and that can serve as a reminder or future study.
First of all, update all packages
# pacman -Syyu
# pacman -S sudo
Create and set password for new user
# useradd -m _username_
# passwd _username_
Set permissions for the new user
# usermod -a -G wheel,storage,power,audio _username_
Then, edit /etc/sudoers, uncomment %wheel ALL=(ALL:ALL) ALL
Reboot and login with your new user
$ pacman -S xorg-server
Edit or create ~/.xprofile, then set Xorg keyboard layout
# setxkbmap br
$ pacman -S xfce4
$ pacman -S lightdm lightdm-gtk-greeter lightdm-gtk-greeter-settings
$ systemctl enable lightdm
$ pacman -S xdg-user-dirs
# xdg-user-dirs-update
$ pacman pulseaudio xfce4-pulseaudio-plugin pavucontrol
Improving the audio (available in Tuning PulseAudio)
Edit /etc/pulse/daemon.conf, uncomment the following lines
high-priority = yes
nice-level = -11
realtime-scheduling = yes
realtime-priority = 5
Uncomment too, but change the value to 10 (old value is 1)
resample-method = speex-float-10
Reboot
$ pacman -S bash-completion htop neofetch
XFCE extra group packages available in xfce4 goodies
$ pacman -S xfce4-clipman-plugin xfce4-whiskermenu-plugin xfce4-screenshooter xfce4-screensaver
$ pacman -S --needed git base-devel && git clone https://aur.archlinux.org/yay.git && cd yay && makepkg -si
# yay orchis-theme breeze-default-cursor-theme tela-circle-icon-theme-grey
$ pacman -S mousepad
$ pacman -S ristretto
$ pacman -S network-manager-applet
$ pacman -S thunar-archive-plugin gvfs
$ pacman -S rxvt-unicode