From your Gmail account, you can choose to automatically and immediately include your signature in every new email you compose.

❶Access your Gmail settings

From Gmail, click on your settings, then See all settings.

❷Access your general settings

From the General tab in the menu, you will find at the bottom of the page the options regarding your signature.

Check the box: Insert the signature before the quoted text in replies and remove the '--' line that precedes it.

That's it!