To change most defaults:
Most system-wide preferences are in System Preferences, which is under the Apple menu. That includes a panel called "Keyboard & Mouse", which lets you change keyboard shortcuts for menut items in Cocoa applications (e.g., Safari, Mail, Pages, Keynote, Numbers, Create). Most other preferences for an individual application are set in a Preferences item in the application menu, the menu with the application's name.
To change the application that opens a document:
To make tooltips appear faster or slower:
Open Terminal (inside /Applications/Utilities) then type this phrase, followed by a return:
The number 400 is the length of the delay in milliseconds. You can choose any delay. Apple's default is 1000. This will work with any Cocoa application, although you may need to restart an application that is running.