Skype doesn’t launch with OS X and doesn’t appear to have an option, unlike many other programs, to do this.
However, after some searching I did find a reference to user preferences that allow you to modify which programs start with
- Press and select “System Preferences”
- Click on “Users & Groups” (bottom left, in the “System” section)
- The current user should be highlighted on the left. To the right, select the “Login Items” tab
- It now lists all the applications that start when the system does. Those ticked will be hidden (click on the screenshot at the side to see my screen)
- Press the + and – button to add and remove applications. To add Skype simply press + and select it from the Applications list.