Raspberry Pi Quick Guide

Below are some basic commands which you need to know to PLAY with raspberry pi

How to install softwares/packages in raspberry pi ?
sudo apt-get install packagename

How to remove softwares/packages in raspberry pi ?
sudo apt-get --purge remove

How to update/upgrade raspberry pi
sudo apt-get update && sudo apt-get upgrade

How to go to GUI mode in raspberry pi ?
startx

How to give root access to pi ?

sudo su

How to see all packages installed in raspberry pi?

dpkg -l

How to change password/memory split /time in raspberry pi?

sudo raspi-config

How to see list of devices attached to raspberry pi?

df -h

How to see all services in raspberry pi ?
service  --status-all

How to stop any service in raspberry pi ?
service mysql stop

How to Disabe unwanted services in raspberry pi? 

update-rc.d  mysql disable
 

How to keep raspberry pi up to date? 

Source
    Install software needed to perform the update:
        pi@raspberrypi:~$ sudo apt-get install ca-certificates git-core binutils
    Download the script:
        pi@raspberrypi:~$ sudo wget https://raw.github.com/Hexxeh/rpi-update/master/rpi-update
    Copy the script to /usr/local/bin:
        pi@raspberrypi:~$ sudo cp rpi-update /usr/local/bin/rpi-update
    Make the script executable:
        pi@raspberrypi:~$ sudo chmod +x /usr/local/bin/rpi-update
    Run the script:
        pi@raspberrypi:~$ sudo rpi-update
        In the future to check for updates, just execute this last step!

How to Change owner/Group in raspberry pi?
chown -R pi
chgrp  -R pi

How to see what all ports are bind in raspberry pi ?
sudo netstat -an|less