1. Go to Settings at the top right corner of your Gmail page
3. Find Signature tweaks feature and enable it by selecting the radio button against Enable button
Opened message would look something like below:-
When you click to Reply or forward the message, you would see your Signature at the top of the original message sent by the sender (in this example Sanjeev)
Note: When this Signature tweaks Gmail Labs feature is enabled, it also removes — appearing before the quoted text in your signature. By default Gmail places two – (–) before the quoted text block of your signature.