There is a Different kind of GSM module Available in Market but Most popular Module is SIM900 so I used SIM900 and Arduino Uno in this Tutorial.
Gsm Modules Manufactured by different companies so most of the GSM modules Require 12v Dc input power Supply but some of them Require 15 v Dc so don’t forget to check the input voltage for the Gsm module you are using.
Insert Your SIM card to Module and Lock it carefully
Connect Power adapter and Turn On the Module
Now wait for some time because it will take some time to establish connection with BTS
When the Module Connection established successfully with the Mobile network so the present status led on Gsm Module board will blink continuously every 3 seconds.
you can check the Gsm module that it,s working fine or Not by making a call on that number which you insert on Gsm module if you hear a ringback it means the Gsm module is good and established a successful connection with the Mobile network.