How can I completly clear all browser history, caches, and keychain passwords? Borrowed a laptop from a friend and would like to clear all internet history and clear all flash caches etc, and forget passwords from the keychain (if it stores these?)

Been using incognito mostly but yeah, and weird cookies stored in a random subolder or anything?

Thanks in advance!
If you're using Safari, go to Safari -&gt; Reset Safari and select check every box. Then click reset. 

If you're using Chrome, click Cmd-Shift-Del and check the desired boxes. Here's an image:



Hope this helps!