Stopping programs from auto-starting?

[kat.hayes]

Skype and Dropbox auto-start when I boot my Mac and I can not find a preference to stop it. How can I turn them from auto-starting through Mac OS?
Thanks.

 

[talmy]

For Dropbox, click the icon in the menu bar (top right of display), click on "Preferences...", and uncheck the box "Start Dropbox on system startup" on the General Pane.

I don't know about Skype.